CLEAR and SOURCE are now bounded.
Assert that SOURCE and CLEAR aren't passed to these functions.
Assert that SOURCE and CLEAR aren't passed to these functions when there is a mask.
Do fixups for SOURCE and CLEAR as well as unbounded operators, since in the absence of a mask, we need SOURCE to work correctly (don't care about CLEAR)
_cairo_ft_font_show_glyphs) Consistently use CLEAR/TRANSPARENT (source doesn't matter) rather than SOURCE/TRANSPARENT when clearing rectangles.
src/cairo-xlib-surface.c src/cairo-surface.c: Use IN rather than SOURCE as an example of an unbounded operator in docs.
Remove CLEAR/SOURCE columns since they are no longer unbounded.
test/operator-clear.c test/operator-source Makefile.am: Add targetted tests of CLEAR/SOURCE.
