libavutil/thread.h: Support OS/2 threads

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
libavutil/threads.h: correct an include to be local

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avutil/buffer: Move USE_ATOMICS to thread.h to avoid it becoming out of sync with it

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avutil/ppc/util_altivec: add () to VEC_SPLAT16 macro

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ac3enc: Use avpriv_float_dsp_alloc()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/aacenc: Use avpriv_float_dsp_alloc()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/on2avc: Use avpriv_float_dsp_alloc()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>