r600g: support all channels of TGSI_FILE_ADDRESS

It's allowed in SM3.
r600g: implement TGSI_OPCODE_BREAKC
r600g: HW bug workaround for TGSI_OPCODE_BREAKC
r600g: remove assert on draw with count == 0
gallium: create TGSI_PROPERTY to disable viewport and clipping
r600g: use TGSI_PROPERTY to disable viewport and clipping

Signed-off-by: David Heidelberger <david.heidelberger@ixit.cz>