i965: Store floating point mode choice in brw_stage_prog_data.

i965: Store floating point mode choice in brw_stage_prog_data.

We use IEEE mode for GLSL programs, but need to use ALT mode for ARB
programs so that 0^0 == 1.  The choice is based entirely on the shader
source language.

Previously, our code to determine which mode we wanted was duplicated
in 8 different places (VS and FS for Gen4-5, Gen6, Gen7, and Gen8).
The ctx->_Shader->CurrentProgram[stage] == NULL check was confusing
as well - we use CurrentProgram (non-derived state), but _Shader
(derived state).  It also relies on knowing that ARB programs don't
use gl_shader_program structures today.  The compiler already makes
this assumption in a few places, but I'd rather keep that assumption
out of the state upload code.

With this patch, we select the mode at compile time, and store that
choice in prog_data.  The state upload code simply uses that decision.

This eliminates a BRW_NEW_*_PROGRAM dependency in the state upload code.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>