lavc/libx264: Fix compilation with libx264 version < 142.
avcodec/hevc: fix chroma transform_add size

Fixes accessing misaligned address
Fixes: signal_sigsegv_1feb99c_10_signal_sigsegv_2d1d35c_79_cov_691940146_EXT_A_ericsson_3.bit

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>