Update lexer to be more JFlex friendly

I've tried to use the lexer with JFlex (Java version of Flex). I've made some changes to it, and after doing a diff with the old one on the generated code, there is no differences except for the rogue semicolon on the `--=` rule.

I still have problems with the `isuf` and `usuf` rules (that syntax is not valid in JFlex), but changing them to be `isuf=i8|i16|i32|i64|i` doesn't generate the same code, although after testing it looks like it's working.

If this can be accepted and somebody can help with the rest of my issues, that will be great :)