Some updates for MacOS building. There is a new getShareDir() function
which the localedir function uses. Hotkeys are now based off
getShareDir() instead of using the SHAREDIR define. Having the single
getShareDir() lets FontForge move in the filesystem provided that the
one getShareDir() is updated to know about this.
Merge pull request #187 from monkeyiq/2013janmac1

Some updates for MacOS building including a new getShareDir() function.