VAAPI: Fix VPP compile if libva is too old
dvdplayer: Allow multithread decoding for hi10p content by default

This allows decoding of some hi10p material on e.g. AMD Fusion with
both cores at the max. This introduces a new advancedsetting named
disablehi10pmultithreading to disable hi10p decoded multithreaded.
fixed: when doing a format conversion from float to 32 bit int, multiply with INT32_MAX - 127, since this is the maximum value that can be stored in 32 bit float and int, if INT32_MAX gets converted to float, it gets rounded to INT32_MAX + 1 which can cause wrap around distortion
rename: MUL32 -> AE_MUL32