|frame_size_enum| in tests/test_opus_encode.cl:117 is flagged as potentially
uninitialized but get_frame_size_enum() will fail anyway if a valid value is
not found.
Newer versions of MSVC are unhappy with the strategy of the build
environment redefining "inline" (even though they don't support the
actual keyword). Instead we define OPUS_INLINE to the right thing
in opus_defines.h.
This is the same approach we use for restrict.
