Fix warnings

This fixes some harmless but annoying warnings. Don't hesitate complaining about cosmetics or whatnot, I'll make any changes requested.

- first commit is to avoid using local variables or method parameters that conflict with member functions
- second is marking static functions as such.
- third commit removes some misplaced ;'s

with these in place, opm-parser now compile warning free on my gcc 4.8 (ubuntu 14.04 box).