Adapt to Chris changes for multithreading.

Chris removed the naked static pointer to fgLogger in
bf35e4fd98458baa5f3a8f3507f73bae4524739c however there are a few places
where it was used. This should address all the remaining issues.
Merge pull request #20 from ktf/fix-fglogger

Adapt to Chris changes for multithreading.