Fix a hangup problem under load of multiple disk xfers on NetBSD hosts.
 - fix a "fallback implementation of counting semaphores with mutex+condvar":
http://git.qemu.org/?p=qemu.git;a=commit;h=c166cb72f1676855816340666c3b618beef4b
976
  - waiting threads are not restarted properly if more than one threads
    are waiting unblock signals in qemu_sem_timedwait()
  - possible missing pthread_cond_signal(3) calls when waiting threads
    are returned by ETIMEDOUT
 - fix an uninitialized variable
Discussed with and patch is provieded by soda@.

XXX: configure should check if the target system has sem_timedwait(3)
     to switch this fallback implementation since sem_timedwait(3) has
     been added in NetBSD -current:
     http://mail-index.NetBSD.org/source-changes/2012/03/08/msg032625.html
     http://mail-index.NetBSD.org/source-changes/2012/03/08/msg032626.html

Bump PKGREVISION.
Updated emulators/qemu to 1.4.2nb1