Vary parsing options in the unit tests to increase code coverage.

http://code.google.com/p/esprima/issues/detail?id=388
Minimize object construction when tracking location.

As suggested by ZHANG Bei <ikarienator@gmail.com>, there is no need for
rich object when tracking the node location. Firefox 20 shows 6% speed-up on
the full benchmarks.

https://code.google.com/p/esprima/issues/detail?id=424