Fix SPARC assembly for 64-bit

Fix SPARC assembly for 64-bit

- The test for whether or not we're building for 64-bit is '#ifdef __arch64__'.
 This appears to be correct on both Linux and Solaris.

- The test for Solaris is now '#if defined(SVR4) || defined(__SVR4) ||
defined(__svr4__)'.  GCC 3.4.0 has all three defined on Solaris 9.

- Enables assembly language clip routines.

- Fixes to make GLSL code build on Solaris.

- Update gl_SPARC_asm.py.