Fix ReferenceError in compiler passes.

Previously, the report-left-recursion and report-missing-rules passes
used PEG.GrammarError without requiring it, causing a ReferenceError.

Since requiring lib/peg.js would cause circular requirements, this
commit imports lib/grammar-error.js as GrammarError.

The bug was introduced in commit
4cda79951a2b502dd6d1c0df8fe2ed45464bb9b7.

Fixes GH-135.
Merge branch 'master' of https://github.com/dmajda/pegjs
Merge pull request #135 from hyperpape/master

PEG.GrammarError is undefined in report-missing-rules and report-left-recursion