add x264 to configure.ac #108

Job	Run time
code formatting check	34s
cppcheck	18m 57s
min features with gcc	3m 37s
min features with g++	3m 1s
min features with clang	3m 24s
max features with gcc	4m 27s
max features with g++	2m 57s
max features with clang	4m 17s
max features with clang and AddressSanitized	4m 0s
max features with gcc and DEBUG	3m 39s
max features with gcc for 32-bit arch (legacy OS)	1m 33s
max features with g++ for 32-bit arch (legacy OS)	1m 38s
max features with clang for 32-bit arch (legacy OS)	1m 59s
	54m 3s

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