names "DUMMYUNIONNAME" and "DUMMYSTRUCTNAME" for anonymous unions and
structs. Support const and extern definitions. Retain tokens (and
whether numbers are hex or not) used for computing constant
expressions, so that the full expression can be written to the header
file instead of the computed integer result of the expression. Parse
the sizeof() operator.  Compute and remember constant definitions and
enum values so they can be used in expressions. Improved identifier
lookup speed. Fixed some bugs.