Patch from Melchior Franz:

Patch from Melchior Franz:

This patch eliminates about 10 of valgrind's "Use of uninitialised
value of size ..." messages. They are all caused by approachlist building
incomplete FGApproach class instances and then copying them into the
approchlist container, hence copying data garbage.
   I know, I couldn't win a beauty contest with this patch, but the
alternative approach -- letting operator<< always leave complete
entries -- didn't look any better. And I do only add those seemingly
useless initialization where the values would be used uninitialized
else. The constructors are only run during setup and won't slow fgfs
down at runtime.