[Pixman] pixman: wasm support

[Michael Meeks]

Hi all,

	We're just building Collabora Online for WASM - where we bundle 
libpixman and cairo - quite possibly we are stepping into a world of 
pain being early to the party here: would love some thoughts on that.

	Either way we seem to hit:

bits_image_fetch_affine_no_alpha_32
general_composite_rect
pixman_image_composite32

	very hard, which is some very large chunk of our profile; and (I guess) 
the obvious question is - has anyone else done the work to tweak for 
WASM intrinsics? advice much appreciated.

	Thanks !

		Michael.
-- 
  michael.meeks at collabora.com  <><, Pseudo Engineer, itinerant idiot