Fix LogFunc via trampoline that corrects the arity
Fix LogFunc via trampoline that corrects the arity

Instead of LogFunc (old) and LogFunc2 (new, correct), keep the existing
API and use a trampoline to go between LogFunc and LogFunc2. This
avoids marking anything as Obsolete, and preserves the old API exactly.

sillsdev/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp