check consistency of glyph counts on input and output, and document it
prevent RemoveUnused from removing slots that the encoding requires

If you want to do that, you should re-encode first.  Note that it already
wouldn't remove any slots before the last used slot, so it's clear that this
command would never have been able to *really* remove all unused slots in
encodings that required them to remain.  Its intended use seems to have been
for removing unused unencoded slots at the end.
tighten up some boundary cases
check consistency of glyph counts on input and output, and document it
prevent RemoveUnused from removing slots that the encoding requires

If you want to do that, you should re-encode first.  Note that it already
wouldn't remove any slots before the last used slot, so it's clear that this
command would never have been able to *really* remove all unused slots in
encodings that required them to remain.  Its intended use seems to have been
for removing unused unencoded slots at the end.
tighten up some boundary cases
Merge branch 'check_glyph_count' of github.com:mskala/fontforge into check_glyph_count
Merge pull request #520 from mskala/check_glyph_count

Check consistency of encoding slot counts on input and output, and document it