gdbm: Update to version 1.20

gdbm: Update to version 1.20

- Update from 1.8.3 (2002) to 1.20 (2021)
- Update rootfile
- There is no longer a make process for make install-compat
   To have the compat libraries you have to add --enable-libgdbm-compat to the configure
   command but then you don't get the non compat libraries.
   So the full configure, make, make install has to be run twice with
   --enable-libgdbm-compat added to the second instance.
- Both static and shared libs are built by default so added --disable-static to both
   build instances
- Nothing flagged from find-dependencies run against the old library versions
- Changelog is too large to include here but full details can be found from the
   ChangeLog file in the source tarball.

Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>