Make Doxygen ignore PHYSFS_DEPRECATED.

docs/Doxyfile

@@ -877,7 +877,8 @@ INCLUDE_FILE_PATTERNS  =
 # omitted =1 is assumed.
 
 PREDEFINED             = DOXYGEN_SHOULD_IGNORE_THIS=1 \
-                         PHYSFS_DECL=
+                         PHYSFS_DECL= \
+                         PHYSFS_DEPRECATED=
 
 # 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.