in `The M4 Macro Processor', by Kernighan and Ritchie.
* `|' and `||' are both logical or. There is no binary or.
* `&' and `&&' are both logical and. There is no binary and.
* `!' has a much higher precedence.
* The equal and relation operators have the same precedence.
* `**' is implemented, and `^' is for exponentation (not xor).
* Unary `+' in implemented.
I've coded exponentiation to return what appears to be the same results
that other versions of m4 return.
bug:if there are multiple files on the command line, file index is not
reset properly, ie. it falls off the side. sigh. also, somewhere along
the line, i again lost the proper m4wrap/autodiversion semantics
[sorry, eric. :-|] but fixed with this patch.
