[PATCH][BZ #14188] Allow pthread_cleanup_push to build with compilers other than gcc

[Roland McGrath]

This is the only use of __builtin_expect in a public header now.
But it seems reasonably likely that we'll have others eventually.
So my inclination would be to put the macro in sys/cdefs.h and give
it a different name.  (Or perhaps also slightly different semantics,
e.g. __glibc_unlikely(BOOL).)


Thanks,
Roland