Add symbolic arithmetic operators
Use variable argument macro for MATCH

Simplified syntax for MATCH expressions.  Now its

  (MATCH X
    (CASE ...)
    (CASE ...)
    ...
    (CASE ...))

instead of

  (MATCH X (
    (CASE ...)
    ...
    (CASE ...)))

Note the absense of the extra set of parentheses around the list of CASE
expressions.
Add FLATTEN to Util.lso
Add reduction function as argument to CFGPARSE

Instead of hard coding the building of a parse tree having the form:

  ((LHS . RULENUM) ... children ...)

a function may now be supplied which accepts the child parse trees
(already reduced by this same function), the LHS symbol, and the
RULENUM and returns the node to supply to higher levels of the parse
tree.