* objc/objc.h (__GNU_LIBOBJC__): New #define providing an easy way
to check the API version. Added some comments.
* objc-private/common.h: New file.
* NXConstStr.m: Include objc-private/common.h.
* Object.m: Same change.
* Protocol.m: Same change.
* archive.c: Same change.
* class.c: Same change.
* encoding.c: Same change.
* exception.c: Same change.
* gc.c: Same change.
* hash.c: Same change.
* init.c: Same change.
* libobjc_entry.c: Same change.
* linking.m: Same change.
* misc.c: Same change (and added a comment).
* nil_method.c: Same change.
* objects.c: Same change.
* sarray.c: Same change.
* selector.c: Same change.
* sendmsg.c: Same change.
* thr.c: Same change.
From-SVN: r164218
Nicola Pero