Fixing issue with loc/range when the loc/range

Summary:https://code.google.com/p/esprima/issues/detail?id=501
markStart() was not always preceded by skipComment(). Moving the
skipComment() inside instead.
Esprima: https://github.com/ariya/esprima/commit/8ff4c56f8248394b249351ef1db3c52348ad38d9#diff-7c9336e4324ea31118ce749be055b6a3R3518