Implement more GLSL instructions

[Ivan Gyurdiev]

> As of this patch, Wine now supports more opcodes in GLSL than
> ARB_vp/fp and we can handle many of the shader 2.0+ instructions not
> available before.  There are a few missing texture operations compared
> to ARB still, and we're not properly handling textures for any shaders
> <2.0, but that's true in ARB as well.
Yes, the missing texture operations are kind of important, I think [ but 
they are valid in SM 1.x only ].
Other suggestions I have:
- fix swizzle, make it work consistently across all instructions (see cmp).
- may be a good idea to centralize casting in one place to avoid 
failures [ yes, I probably should have done that when adding casting in 
my patch :)
- merge the rest of the SHADER_ARB code, and organize it the same as the 
SHADER_GLSL code (in arb_shader.c or something like that). Then go 
through and compare the two and make sure modifiers and other such 
things work the same way.

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For 1.x texture support we could delay compilation until we know what 
kind of textures will be bound, and then recompile if textures change 
their dimensionality [ which hopefully they won't ].