Undefine _PR_POLL_AVAILABLE for pthreads.  libc_r doesn't have poll().  The poll() in libc is not thread-safe, so we can't use it with pthreads.  This patch is contributed by Jeremy Lea <reg@shale.csir.co.za>.
Undefine _PR_POLL_AVAILABLE for pthreads.  libc_r doesn't have
poll().  The poll() in libc is not thread-safe, so we can't use
it with pthreads.  This patch is contributed by Jeremy Lea
<reg@shale.csir.co.za>.

makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub,makotokato/nsprpub