Workaround for MSVC not optimizing away Write() in GeneratePixelShader

ShaderConstantProfile and ShaderUid now have an empty implementation
of Write() that uses variadic templates instead of varargs. MSVC is now
able to inline and optimize away this when necessary.
Added __forceinline to AlphaTest::TestResult() to make MSVC inline it
Merge pull request #1308 from kayru/shader_generator_write_opt

Workaround for MSVC not optimizing away Write() in GeneratePixelShader