Resolve active render target in D3D9 before switch

On D3D9 platforms that work on active render target instead of
a specified surface, the resovle of the previous RT must happen
before the new RT becomes active.
Merge pull request #140 from mendsley/resolve

Resolve active render target in D3D9 before switch
Cleanup.
Fixed clang warning: equality comparison with extraneous parentheses.
Disabled clang warnings in glsl-optimizer.
Merge branch 'master' of github.com:bkaradzic/bgfx
Disabled unknown pragma warning in GCC.
Fixed initializer order warning.
Added missing linker dependency.
Fixed SAL define and MinGW standard library argument collision.
Cleanup.