Bitwise comparison intrinsics

This patch implements lowering for the F08 bitwise comparison intrinsics
(BGE, BGT, BLE and BLT).

This does not create any runtime functions since the functionality is
simple enough to carry out in IR.

The existing semantic check has been changed because it unconditionally
converted the arguments to the largest possible integer type. This
resulted in the argument with the smaller bit-size being sign-extended.
However, the standard requires the argument with the smaller bit-size to
be zero-extended.

Reviewed By: klausler, jeanPerier

Differential Revision: https://reviews.llvm.org/D127805