fate: vpx: Remove one redundant $(eval) invocation
pthread: Avoid spurious wakeups

pthread_wait_cond can wake up unexpectedly (Wikipedia: Spurious_wakeup).

The FF_THREAD_SLICE thread mechanism could spontaneously execute
jobs or allow the caller of avctx->execute to return before all
jobs were complete.

Test both cases to ensure the wakeup is real.

Signed-off-by: Ben Jackson <ben@ben.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
avio: Use AVERROR_PROTOCOL_NOT_FOUND

When the protocol is missing ffurl_alloc() should return
AVERROR_PROTOCOL_NOT_FOUND instead of AVERROR(ENOENT).

Bug-Id: 577
CC: libav-stable@libav.org