mov: Drop unused parameter from ff_mov_read_esds()

This is cleaner and avoids an uninitialized variable warning with MSVC.
vfwcap: Drop fallback VfW defines

The defines were added long ago when MinGW still lacked them.
vc1: Add missing parentheses to conditions in vc1_decode_b_mb_intfr()
pcm: Drop unused variable from DECODE_PLANAR macro
pcm: Drop av_unused attribute from variable that is always used
vsrc_movie: Avoid a variable indirection in movie_get_frame()

This avoids an unused variable warning with MSVC since the variable is
only used in a debug mode printf statement.