resolve the identifier/typedef-name ambiguity in the parser

[rieske]

http://en.wikipedia.org/wiki/The_lexer_hack
http://www.cs.dartmouth.edu/~mckeeman/references/JCLT/ResolvingTypedefsInAMultipassCCompiler.pdf
https://groups.google.com/forum/#!msg/comp.compilers/gqeQy3mXqnA/tAWGZlt7ecAJ