All 2D coordinate spaces in Cogl have their origin at the top-left so we
shouldn't be flipping the coordinates we pass to
cogl_framebuffer_swap_region to be relative to the bottom of the
framebuffer.
This bumps the Cogl version requirement to 1.7.5 since we've had to fix
a bug in the semantics of cogl_framebuffer_swap_region.
Reviewed-by: Neil Roberts <neil@linux.intel.com>