gltrace: Use a regex for unpack function names.

Less maintenance overhead, less chances of oversight.
glretrace: Use a regex for pack function names.
glretrace: Use regex for map/unmap buffer function names.
specs: Fix glGetFragDataLocation.

It merely returns a static index, not return a swizzleable uniform
location.
glretrace: Ensure all pack functions have side effects flag set.
glretrace: Add a few glBlitFramebuffer* variants to misc draw list.
glretrace: Refactor logic to get active program into a function.