R600: Add basic 64-bit float load support to GPRs

* Added R600_Reg64 class
* Added T#Index#.XY registers definition
* Added v2i32 register reads from parameter and global space
* Added f32 and i32 elements extraction from v2f32 and v2i32
* Added v2i32 -> v2f32 conversions

Signed-off-by: Dmitry Cherkassov <dcherkassov@gmail.com>
R600: Add 64-bit v2f32/v2i32 store

Signed-off-by: Dmitry Cherkassov <dcherkassov@gmail.com>
R600: Add test for 64-bit v2f32/v2i32

Added tests for checking v2f32/v2i32 load, store and element extract

Signed-off-by: Dmitry Cherkassov <dcherkassov@gmail.com>