glsl: Generate ir_expression_operation.h from Python

glsl: Generate ir_expression_operation.h from Python

There are differences in where end-of-line comments are placed, but
'diff -wud' is clean.

v2: Massive rebase.

v3: With much help from José Fonseca, fix SCons build.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Acked-by: Dylan Baker <dylan@pnwbakers.com>