module: unicode: #if out unused bits of libunicode (#13224)

[nabijaczleweli]

Motivation and Context

The second (non-uconv) half of #13224, minus U8_TEXTPREP_NOWAIT, U8_VALIDATE_CHECK_ADDITIONAL, and U8_VALIDATE_UCS2_RANGE (rejected in review below)

Description

The API remains, the removed bits are #ifed out.

$ size -G ./module/zfs.ko ./module/zfs.new.ko
      text       data        bss      total filename
   2865126    1597982     755768    5218876 ./module/zfs.ko
   2864038    1429784     755768    5049590 ./module/zfs.new.ko
     -1088    -168198
       -1k      -164k

How Has This Been Tested?

Builds.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes. — none apply
• I have run the ZFS Test Suite with this change applied. — CI take my hand
• All commit messages are properly formatted and contain Signed-off-by.

[amotin]

Looks better to me, but lets fix style, build and one more comment:

[amotin]

Have no objections, assuming it will pass the tests. Thanks.

[amotin]

  module/unicode/u8_textprep.c: In function 'do_case_conv':
  module/unicode/u8_textprep.c:555:12: error: 'i' may be used uninitialized [-Werror=maybe-uninitialized]
    555 |         u8s[i] = '\0';
        |            ^
  module/unicode/u8_textprep.c:463:16: note: 'i' was declared here
    463 |         size_t i;
        |                ^

[nabijaczleweli]

I don't get this warning but fixed hopefully

[amotin]

I don't know why checkstyle does not complain, but one of your commit messages has too long title. Please reformat. I am also not sure this worth 3 individual commits.