This time with more manual checking and using git blame -M -C, so that
a few cases of copied code get a copyright notice corresponding to
their initial introduction.
The temporary removals for landscape saving purposes now use the temporary
removal code of the solidmasks. SolidMasks remove themselves from the
landscape when deleted. A now superfluous argument to Remove() is removed.
This is a whitespace-only patch. Hopefully, it'll only affect rarely-changed
parts of the engine, since all regularly maintained pieces should already
use tabs.