i965: Introduce a new brw_inst API.

i965: Introduce a new brw_inst API.

This is similar to gen8_instruction, and will eventually replace it.

For now nothing uses this, but we can incrementally convert.
The new API takes the existing brw_instruction pointers to ease
conversion; when done, we can simply drop the old structure and rename
struct brw_instruction -> brw_inst.

v2: (by Matt Turner) Make JIP/UIP functions take a signed argument.
v3: (by Kenneth Graunke)
 - Make Gen4-6 jump target functions take a signed argument.
 - Fix indirect align1 AddrImm bits on Gen4-7.
 - Fix SFID on Sandybridge to use bits 27:24.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> [v1, v3+]
Signed-off-by: Matt Turner <mattst88@gmail.com> [v2]
Reviewed-by: Matt Turner <mattst88@gmail.com>