Log Message:
Change behavior of libpthread handling
* Disable linkage with pthread for FreeBSD/DragonFly/NetBSD, they have
  pthread_* () stubs in libc (it result in same as the previous behavior).
  * but NetBSD<4.99.36 does not have pthread_equal() stub in libc,
    so define weak reference to it.
* Treat OpenBSD and MirBSD same as Linux to avoid linkage with libpthread.
* Others will be linked with pthread, fixes PR 46254.

tested NetBSD-5.1.2, and confirmed fixed on NetBSD-4.0.1 and OpenBSD-5.0.

Bump PKGREVISION.