Adds support for multi-line comments in Matlab

Matlab block comments were not considered previously and the operators %{ and %} were treated as inline comments and all text between those symbols was parsed as if it were code rather than being treated as a block comment.

I have added new checks to the language definition and added the appropriate test files.

The basic rule is that block comments should begin with %{ and end with %} with the specification that %{ and %} must appear on their own lines with only whitespace before or after them on that line.

More information available at the [Mathworks website][http://www.mathworks.com/help/matlab/matlab_prog/comments.html].