glsl: Add IR builder shortcuts for a bunch of random opcodes.

glsl: Add IR builder shortcuts for a bunch of random opcodes.

Adding new convenience emitters makes it easier to generate IR involving
these opcodes.

bitfield_insert is particularly useful, since there is no expr() for
quadops.

v2: Add fma() and rename lrp() operands to x/y/a to match the GLSL
    specification (suggested by Matt Turner).  Fix whitespace issues.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>