r300: Add proper support for sin/cos instruction in fragment program

r300: Add proper support for sin/cos instruction in fragment program

Getting proper SIN and COS wasn't as easy as it appeared.
I had to make make some changes to the fragment program code.
general FP changes:
- support HHH swizzle for vector instructions.
- don't copy a source to a temp when it is not XYZW swizzled, but
 combine the two and have the swizzle resolve any issues.
 (saves temps/instructions with more elaborate shader code)
- fix overflow in cnstv[].