Simplify various loops when scanning for a numeric literal.

This decrease the cyclomatic complexity of scanNumericLiteral down to 14.

http://code.google.com/p/esprima/issues/detail?id=396
Add (optional) input source information to the syntax node.

As suggested by Daniel Dotsenko, we shall support `source` property in
the `loc` object of the syntax node.

This is also a good chance to start using the delegate for each syntax
node processing.

The tests were created by Yusuke Suzuki.

http://code.google.com/p/esprima/issues/detail?id=355
http://code.google.com/p/esprima/issues/detail?id=386