Undo the xmalloc->malloc optimization FreeBSD made in certain cases

Undo the xmalloc->malloc optimization FreeBSD made in certain cases
where xmalloc gets defined to malloc which gets defined to xmalloc which
gets defined to malloc again which gets defined to ... and so on.
Culprits: parser files, gcc/system.h, dragonfly-native.h, and various
Makefile's.

Add [DragonFly] to gcc3's version ident.