Mark all non-opaque formats in OpenGL as non-emulated. Non-opaque 16f are all uploadable in OpenGL and do not involve special code path. Although the driver is emulating the transfer of them, the overall performance of 16f formats is still significantly better than 32f formats.
When comparing formats, only compare important capabilities (i.e., the first six bits) of formats with different depth. This allows selecting a format with lower depth while sacrificing some less important capabilities. It is rare that a format with less important capabilities like PL_FMT_CAP_TEXEL_UNIFORM is required; if so, the caller can explicitly specify it in pl_find_fmt().
Fixes #263
This PR does the following changes:
PL_FMT_CAP_TEXEL_UNIFORMis required; if so, the caller can explicitly specify it inpl_find_fmt().