First steps towards Prolog Cafe compatability.
call_cleanup/2 is not supported by Prolog Cafe. Use custom version.
call/2-... is not supported by Prolog Cafe. Luckily, meta_error can easily use call/1.
Modified the entire program to use codes instead of chars.
Finished conversion to use double_quotes codes, added a replacement for code_type, used debug_msg in code.
Re-organized Prolog Compat library into common predicates (replacements for SWI builtins) and compat predicates (must be loaded only when not using SWI-Prolog).