glsl/ast: Add 64-bit integer support to conversion functions

glsl/ast: Add 64-bit integer support to conversion functions

This adds support to call the new operations on conversions.

v2 (idr): Delete an unnecessary break-statement.  Noticed by Matt.  Add
a missing blank line.  Noticed by Ian.

v3 (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>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> [v1]
Reviewed-by: Matt Turner <mattst88@gmail.com> [v2]
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>