Install data to CDOGS_DATA_DIR

utils.c is searching data files in CDOGS_DATA_DIR, so make sure
that the files are also installed there (similar to CDOGS_DOC_DIR).

CMakeLists.txt

@@ -221,7 +221,7 @@ install(DIRECTORY
 	${CMAKE_SOURCE_DIR}/graphics
 	${CMAKE_SOURCE_DIR}/music
 	${CMAKE_SOURCE_DIR}/sounds
-	DESTINATION ${DATA_INSTALL_DIR})
+	DESTINATION ${CDOGS_DATA_DIR})
 
 if(NOT DEFINED CDOGS_DOC_DIR)
 	set(CDOGS_DOC_DIR "${DATA_INSTALL_DIR}/doc")