The recent change to sparse_bitsets broke the lex library in extras.
Specifically, we now now need to make characters an instance of the
uenum typeclass. This diff does so.
library/char.m:
Add predicates and functions for converting between unsigned integers
and characters.
Make characters an instance of the uenum typeclass.
tests/hard_coded/Mmakefile:
tests/hard_coded/char_uint_conv.{m,exp,exp2}:
Add a test of the above conversions.
NEWS:
Announce the additions.
extras/lex/lex.m:
Conform to recent changes.
