Fix opening UFO fonts with bad openTypeOS2Type key

https://github.com/fontforge/fontforge/issues/448
Remove superfluous new lines
Remove superfluous new lines
Share a bit of code
Don’t output openTypeOS2Type if fsType is -1

We use -1 elsewhere to mean unset.
Merge pull request #453 from JoesCat/master

Fix opening UFO fonts with bad openTypeOS2Type key