Fix wrong model recognition

Parser was recognizing words with `model` keyword combination, for example `` `model` `` or `Cmodel`, as model, this is a suggestion to fix the issue. this pull request would close issue #92 and #152.
@alikh31 either way, please figure it out, you `SYMBOL_IDENTIFIER` in one way or another but it has to be using it so the symbol identifier is defined at one place only