physfs.h: Reworked documentation to be compatible with SDL3's wikiheaders.

This still needs a little work, but this is most of the way there.

docs/Doxyfile

@@ -876,11 +876,11 @@ INCLUDE_FILE_PATTERNS  =
 # or name=definition (no spaces). If the definition and the = are 
 # omitted =1 is assumed.
 
-PREDEFINED             = DOXYGEN_SHOULD_IGNORE_THIS=1 \
+PREDEFINED             = PHYSFS_WIKI_DOCUMENTATION_SECTION=1 \
                          PHYSFS_DECL= \
                          PHYSFS_DEPRECATED=
 
-# If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then 
+# If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then
 # this tag can be used to specify a list of macro names that should be expanded. 
 # The macro definition that is found in the sources will be used. 
 # Use the PREDEFINED tag if you want to use a different macro definition.