playsink: Always take the playsink lock when adding or removing pad probes

Otherwise we might end up inside the callback without having stored
the probe id... then try to remove that probe (not!) from the callback
and wait forever for the pad to unblock.
audioresample: Fix build on x86 if emmintrin.h is available but can't be used

On i386, EMMINTRIN is defined but not usable without SSE so check for
__SSE__ and __SSE2__ as well.

https://bugzilla.gnome.org/show_bug.cgi?id=670690
audioresample: It's HAVE_EMMINTRIN_H, not HAVE_XMMINTRIN_H for SSE2