[Xsb-development] CHR package

[Terrance S. <ts...@cs...>]

This is mostly for Tom.  I made the chr library files into a package and
will add next week a predicate load_chr/1 that will preprocess and or
compile and or load a chr file.  I think that this predicate will prove
more useful than an explicit preprocess shell command -- but let me know
if you want me to keep the chr_pp shell command also.

I also made a change to suppress warnings about singleton variables, and
to use concat_atom rather than XSB's atom_concat.

Terry