Instead of having a script for each cscope database, just specify a list
of directories and have this script generate the list of files.
Rename set_csdb to cscope.
Introduce an editor wrapper called 'edit'. It looks at the file to be
opened and tries to figure out if there's a cscope database associated
with it. If so, it sets CSCOPE_DB automatically.
Rename cscope to cscope.sh to reflect the fact that it's not an
executable script.