Line directive emitted in middle of multiline string

[njnobles]

Attempts to address #225

PR reverts the changes to cpp_iterator.hpp that were introduced in #140

[jefftrull]

Sorry I misunderstood the test situation here, you already thoughtfully provided one as you did for #223!

I'll try to come up with my own fix that doesn't completely revert #140 since I like the refactoring part of it. #170 is the redundant commit (w.r.t this bug).

[jefftrull]

Thanks for all the work you've done on this. It's far more detail than we usually get for bugs, and I appreciate it.
We're going to close this in favor of improving the lexer error checking, rejecting these kinds of constructs entirely.