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.
here is my idea with `SYMBOL_IDENTIFIER`:
`"^([[:blank:]]*" SYMBOL_IDENTIFIER ")?[[:blank:]]+[Mm]odel" MEDIA_TYPE "?[[:blank:]]*$"`
this would increase the number of groups to 5 but it's safe to say it would pass every needed situation.
but I will check if your suggested regex might work as it seems simpler.