NORSPEC-349 make render targets use original formats when resizing impostors and fix alpha for deferred impostor shader

NORSPEC-342 NORSPEC-352 make impostor alpha shader use vertex alpha to remedy unsightly blemishes, boxes, and the occasional extra wing.

NORSPEC-342 add simple pass type to things rendered for impostors to fix missing shoes/belts/handbags/cigarettecases/etc

Fix for NORSPEC 271 - Transparent prims in Materials Viewer are incorrectly affecting depth of field by modifying the depth buffer

NORSPEC-342 WIP MATBUG-347 make impostor rendering not contribute to depth for mostly-transparent buffer pixels, aka hair in ALM only

NORSPEC-346 fix knock-on causing alpha mask edits to cause materials to get removed and revert to alpha blend

NORSPEC-329 fix mangling of diffuse alpha mode by material edits when only one face really has alpha

NORSPEC-304 NORSPEC-336 another attempt as resolving black glow overdraw without breaking glow (even for alpha-blended) faces

NORSPEC-314 fixed another mac-specific stupidity by splitting out a new srgb_mac version of the shader