compiler/const_prop.m:
Replace pairs and maybes with a semantically meaningful type.
Restrict this type to the part we actually use.
Optimize ubits_per_{int,uint} the same way we have long optimized
bits_per_{int,uint}.
compiler/simplify_goal_call.m:
Improve the wording of some warnings.
When constructing those warnings, don't test the value of warn_simple_code
twice.
compiler/uint_emu.m:
Fix copy-and-paste typo.
tests/warnings/unsigned_zero_cmp.exp:
Expect the updated text of the above warnings.
If --warn-simple-code is enabled, then emit a warning for comparisons of
unsigned integer values against zero if that comparison is a tautology or
contradiction.
compiler/simplify_goal_call.m:
Implement the new warning.
tests/warnings/Mmakefile:
tests/warnings/unsigned_zero_cmp.{m,exp}:
Add a test of the new warning.
