We have to use the texture limit of the fragment pipeline in use here,
not the fixed function GL texture limit.

Also adds a simple test for this. In the fixed function and nvrc/nvts
code this already works properly.

There is room for 8 texture coordinates, not just 4.

Since some of those function pointers are direct GL functions the function
prototype needs the WINE_GLAPI calling convention. This makes prevents
drawStridedSlow from crashing with USE_WIN32_OPENGL.

This is done by LoadLocation now.

If we're heading out of the pixelshader handler early, and a pixel
shader is in use, the pixel shader may not be compiled. The vertex
shader handler then checks if the pixel shader is dirty, and calls the
shader backend to apply the shader if it isn't.  Thus, in the case of
GLSL, the shader code could attempt to link an uncompiled shader into
the program. This isn't much of a problem because when the fog is
applied, the pixel shader is compiled and the program re-linked.