Fix font loading so that it works for OSX *and* Linux

On GNU/Linux, the Inconsolata font needs to be loaded with style
"Medium", but on Mac OSX it needs to be loaded as "dz" for who knows
what reason. One more if statement and now it should work fine on both
operating systems.
Put all OS related stuff together

Just moved the new OSX specific stuff up to where all the other OS
specific stuff is set.