VideoCommon: Add in/out qualifiers to centroid storage qualifier.

Fixes shaders for GPUs that don't support GL_ARB_shading_language_420pack.
Merge pull request #1715 from Armada651/geom-interface

VideoCommon: Add in/out qualifiers to centroid storage qualifier.
VideoCommon: Handle wireframe mode in the geometry shader.
D3DState: Remove wireframe rasterizer support.
VideoCommon: Make IsPassthrough() a function of the ShaderUid.
GeometryShaderGen: Re-emit the first vertex when wireframe mode is enabled.