Fix accessibility for menus.

-Menu navigation using arrow keys
-Select File Menu when ALT key is pressed
-Screen-reader feedback glitches

	modified:   mstyle/mstyle.cpp
As far as I can tell this code doesn't do anything on MacOSX. So for me, after a test on Mac and Windows, it can stay like this. If someone on Linux is not happy with it we can make it OS dependent. I'll merge it! Good job!