I had debated putting the blending in the compose subpass or a separate
pass but went with the separate pass originally, but it turns out that
removing the separate pass gains 1-3% (5-15/545 fps in a timedemo of
demo1).
It's a bit flaky for particles, especially at higher frame rates, but
that's due to supporting only 64 overlapping pixels. A reasonable
solution is probably switching to a priority heap for the "sort" and
upping the limit.
This splits up render pass creation so that the creation of the various
resources can be tailored to the needs of the actual render pass
sub-system. In addition, it gets window resizing mostly working (just
some problems with incorrect rendering).
Things are a bit of a mess with interdependence between sub-module
initialization and render pass initialization, and window resizing is
broken, but the main render pass rendering to an image that is then
post-processed (currently just blitted) is working. This will make it
possible to implement fisheye and water warp (and other effects, of
course).
