Added a treetop grammar specification for arithmetic to serve as the basis of a functional test of the grammar parser.
Added a treetop grammar specification for arithmetic to serve as the basis of a functional test of the grammar parser.

git-svn-id: 187a4080048d9d4c52729886a33adbc5b789576d@37 0990e5dc-4a6a-4c17-b0d6-4743f9744c17

nathansobo/treetop,xiaohui-zhangxh/treetop,cjheath/treetop,maddenp/treetop