Support Emacs-style in-buffer syntax settings

GNU Emacs has a useful feature that allows an individual file to override the default Emacs mode (and, hence, the associated language syntax and colorization) by using a special magic string somewhere in the first non-blank line of the file. For instance, if file foo.C would normally be displayed using C syntax rules, but you want to force Sublime Text 2 to use C++ rules, simply include a comment like this in the first non-blank line of the file: