[dwm] little fix

I noticed two bugs (easily reproducible):
1. If you start dwm when you have windows which are defined as
floating in some rule, it won't be raised until you re-focus it.
2. Maximize, in firefox go to youtube and move the mouse pointer to
the video window. Your firefox window will be ugly resized.
The attached patch fixes both issues, but I'm not sure this is the
right way (the right place) to fix it. Further testing could be
necessary.

-- 
- yiyus || JGL .