* m4/extern-inline.m4 (gl_EXTERN_INLINE): Also assume the bug
is present if either __DragonFly__ or __FreeBSD__ is defined.
FreeBSD problem reported by Andrey Borzenkov in:
http://lists.gnu.org/archive/html/bug-gnulib/2014-07/msg00104.html
Also, worry about __APPLE__ only if __MACH__ is also defined,
as this is more consistent with the rest of gnulib.
(_GL_EXTERN_INLINE_STDHEADER_BUG): Rename this internal macro from
_GL_EXTERN_INLINE_APPLE_BUG, since the bug is not limited to Apple.