* render/bgfx: Improved clearing and blending. Added prescale support. Fixes MT07586, MT07587, MT08084.
* render/bgfx: Fixed blend and tint handling. (Fixes Github #1953).
* render/bgfx/blendreader.cpp: Support non-separated blend mode specification for BGFX effects.
* render/bgfx: Reworked how horizontally-padded screen textures are handled. Likely fixes MT08512 and MT08505.
* render/bgfx: Ensure that a texture's width margin is updated in all cases.
* render/d3d/d3dhlsl.cpp: Fixed tinting in HLSL post-processing mode.
* render/d3d/d3dhlsl.cpp: Avoid most redundant state-setting calls. Reduces D3D API calls by about 90% on fruit machine drivers.
* render/d3d/d3dhlsl.cpp: Assign SourceDims and QuadDims uniforms to only those effects that use them.
* machine/laserdsc.cpp: Always add video quad to screen container, adjust tint based on m_videoenable instead.
