video/fmt-conversion, img_format: change license to LGPL

The problem with fmt-conversion.h is that "lucabe", who disagreed with
LGPL, originally wrote it. But it was actually rewritten by "reimar"
later. The original switch statement was replaced with a lookup table.
No code other than the imgfmt2pixfmt() function signature survives.
Neither the format pairs (PIXFMT<->IMGFMT), nor the concept of mapping
them, can be copyrighted.

So changing the license should be fine, because reimar and all other
authors involved with the new code agreed to LGPL.

We also don't consider format pairs added later as copyrightable.

(The direct-mapping idea mentioned in the "Copyright" file seems
attractive, and I might implement in later anyway.)

Likewise, there might be some format names added to img_format.h, which
are not covered by relicensing agreements. These all affect "later"
additions, and they follow either the FFmpeg PIXFMT naming or some other
pre-existing logic, so this should be fine.

Copyright

@@ -300,12 +300,11 @@ x   video/decode/dec_video.*        hard
     video/filter/vf_vdpaupp.c       LGPL
     video/filter/vf_yadif.c         will be deleted
     video/csputils.*                LGPL
-x   video/fmt-conversion.*          hard
-        (required for LGPL core: might direct-map them to AV_PIXFMT or so)
+    video/fmt-conversion.*          LGPL
     video/gpu_memcpy.*              will be deleted
     video/hwdec.*                   LGPL
 x   video/image_writer.*            unknown
-x   video/img_format.*              hard
+    video/img_format.*              LGPL
     video/mp_image.*                almost LGPL
     video/mp_image_pool.*           LGPL
     video/out/aspect.*              LGPL

video/fmt-conversion.c

@@ -1,18 +1,18 @@
 /*
  * This file is part of mpv.
  *
- * mpv is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
  *
  * mpv is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * GNU Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License along
- * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <libavutil/pixdesc.h>

video/fmt-conversion.h

@@ -1,18 +1,18 @@
 /*
  * This file is part of mpv.
  *
- * mpv is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
  *
  * mpv is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * GNU Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License along
- * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef MPLAYER_FMT_CONVERSION_H

video/img_format.c

@@ -1,18 +1,18 @@
 /*
  * This file is part of mpv.
  *
- * mpv is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
  *
  * mpv is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * GNU Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License along
- * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <assert.h>

video/img_format.h

@@ -1,18 +1,18 @@
 /*
  * This file is part of mpv.
  *
- * mpv is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
  *
  * mpv is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * GNU Lesser General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License along
- * with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef MPLAYER_IMG_FORMAT_H