R600: Add support for indirect addressing of non default const buffer

NOTE: This is a candidate for the Mesa stable branch.
R600: Use MUL_IEEE for trig/fdiv intrinsic

Reviewed-by: Tom Stellard <thomas.stellard at amd.com>
R600: CONST_ADDRESS node is not marked as mayLoad anymore

Reviewed-by: Tom Stellard <thomas.stellard at amd.com>

mayLoad complexify scheduling and does not bring any usefull info
as the location is not writeable at all.
R600: Turn BUILD_VECTOR into Reg_Sequence

Reviewed-by: Tom Stellard <thomas.stellard at amd.com>
R600: Remove LowerConstCopyPass and lower CONST_COPY right after ISel.

Maintaining CONST_COPY Instructions until Pre Emit may prevent some ifcvt case
and taking them in account for scheduling is difficult for no real benefit.