Bug report by Hongxu Chen.

Bug report by Xuezhi Yan.

Result was never used in that case.

Some hardware decoders reject to decode streams with non-zero
constraint_set4_flag/constraint_set5_flag.

pkg-config doesn't like spaces in version string.

Henrik Gramner authored Mar 30, 2019 and Anton Mitrofanov committed Jul 17, 2019

Simplifies a lot of code and avoids having to export public asm functions.

Note that the force_align_arg_pointer function attribute is broken in clang
versions prior to 6.0.1 which may result in crashes, so make sure to either
use a newer clang version or a different compiler.

Removes need for -Bsymbolic during linking.

Fix crash of MSVC builds compiled with --system-libx264 and /MT (default) CRT.