kern freefonts

After some trial and error, I have determined that I can get both FreeSerif and FreeSans to kern on Linux and Windows under Qt 5.3 (and apparently Qt 5.3 as well) by building them from the ".sfd" sources with OpenType turned *off*.  Mac, as far as I know, still requires that option to be turned *on*, unless that requirement has gone away with Qt 5.4.

This PR includes the latest ".sfd" sources (two years old, but apparently still newer than what we were using) and ".ttf" files I generated using FontForge.  There are two TTF versions of each font - the regular version for Linux & Windows, and the "-Mac" version that I *assume* will kern on Mac whereas the regular version probably won't.  I didn't change the makefile because I have no way of testing that.