Free extensions only if there were initialized, i.e. GIF was opened . Fix bug #1752
libtiff does not handle well finding a TIFFTAG_PREDICTOR in uncompressed images so we won't ask it unless DEFLATE is being used. Fix bug #1753
Ensure that 'gdip_get_cairo_font_face' always returns a FreeType font.

When compiling Cairo on the Mac, both the Quartz and FreeType font
backend have to be enabled. Since the Quartz backend takes precedence,
'cairo_get_font_face' will return a Quartz font, which causes
'gdip_get_fontfamily_details' to fail (See
'cairo_ft_scaled_font_lock_face').

By using 'cairo_ft_font_face_create_for_pattern', we ensure that we
always get back an FT_Face.
Don't link with xrender on OSX.
Bump the version number to 2.10.8.
Merge tag '2.10.8' into develop