Fix the issue when the loc/range would sometimes include a leading whitespace.

Summary:https://code.google.com/p/esprima/issues/detail?id=501
markStart() was not always preceded by skipComment(). Moving the
skipComment() inside instead.

Test Plan: npm test
Update jQuery Mobile in the benchmark corpus to version 1.4.2.

https://code.google.com/p/esprima/issues/detail?id=354