Added accessor macros to clean up tedious code.
Another macro for a bit of cleanup
formatting
Added RETURN_ERR to clean up lval_del + return lval_err pattern.
Added LOOKUP and SUBSTR to clean up function name lookup/comparison.
Finished up ch10. Seems to work, but I HATE the implementation. The
fact that most of the sexp functions are destructive is terrible,
horrible, no good, very bad code.