r600 : check in shader code test enable flag: if flag

r600 : check in shader code test enable flag: if flag
R600_ENABLE_GLSL_TEST defined, IL shader code will goto r600 assembler.
The test base is /mesa/progs/glsl/brick, and changes
shader code in CH06-brick.frag/vert to test different logic op
combination. (if,else,while,function,...). The stack depth code is not
in yet, so it is hard coded now. So complex code would not run (such as
things like 8 loops embeded loop in loop).