el/dot-emacs.el (mdw-fill-paragraph): Pass on arguments faithfully.

The JUSTIFY option doesn't work very well when the fill prefix has
trailing whitespace, but that's a reason not to use it as a user, not
for suppressing it.  The REGION behaviour seems potentially useful, so
suppressing it was undoubtedly a mistake.  (Compatibility isn't an issue
here: both arguments have been around since at least Emacs 23.)