glsl/ir: Add support for 64-bit integer conversions.

glsl/ir: Add support for 64-bit integer conversions.

This adds all the conversions in the world, I'm not 100% sure of all of
these are needed, but add all of them and we can cut them down later.

v2: fix issue with packing output types.

v3 (idr): Rebase on top of idr's series to generate
ir_expression_operation_constant.h.  Fix transposed ir_validate
assertions for ir_unop_u642i64 and ir_unop_i642u64.  Add missing
automatic type setup for ir_unop_u642i64 and ir_unop_i642u64.

v4 (idr): "cut them down later" => Remove ir_unop_b2u64 and
ir_unop_u642b.  Handle these with extra i2u or u2i casts just like
uint(bool) and bool(uint) conversion is done.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> [v2]
Reviewed-by: Matt Turner <mattst88@gmail.com> [v3]
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>