Further changes to selectable H.264 support #476

Job	Run time
cppcheck	18m 41s
code formatting check	16s
min features with gcc	3m 14s
min features with g++	2m 37s
min features with clang	2m 51s
max features with gcc	3m 53s
max features with g++	2m 45s
max features with clang	3m 50s
max features with clang and AddressSanitized	3m 25s
max features with gcc and DEBUG	2m 34s
max features with gcc for 32-bit arch (legacy OS)	2m 3s
max features with g++ for 32-bit arch (legacy OS)	1m 32s
max features with clang for 32-bit arch (legacy OS)	2m 15s
	49m 56s

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