New method of handling quotes and comments that examines lines character by character like most languages do, instead of just searching for the start of a comment.  If a comment character is inside a quoted string, it will not kick off a new comment.  (This actually fixes the core design flaw that caused semicolons to truncate messages, so the $semicolon tag is technically no longer necessary.  It will still be kept, of course.)
Fixes Mantis #3001.

git-svn-id: svn://svn.icculus.org/fs2open/trunk@10492 387891d4-d844-0410-90c0-e4c51a9137d3