Add line number to NameError when the line number is available.
Better way of handling line numbers in loadname.

The previous method did not pass when run through the google compiler.  Ooops.
Clean up warning.  No change to skulpt.js or builtin.js
Roll back the changes that added line numbers to NameError

There is an easier and more consistent way to add this to the runit wrapper function used by skulpt applications.  Maybe there is a way to add this same level of consistency to the skulpt core.  But for now, it seems safer to roll back this change and grab the line numbers in the wrapper.