various seeking fixes
fix segfault for image2 formats
combined stream seek methods
allow unkown codecs
added LDFLAGS and CFLAGS overrides
release the gil on potentially blocking operations
exposed sws_getColorspaceDetails, sws_getCoefficients and sws_setColorspaceDetails
added colorspace conversion options
don't reformat if format matches
simplified __getbuffer__
fix for sws_getColorspaceDetails if pix_fmt conversion not supported