Instead of GRAMPSHOME. GRAMPSHOME is based on the assumption that
the config directory is GRAMPSHOME/gramps, and that causes the
default location for reports and backups to be ~/Library/Application Support.
The MSWin variables allow the two to be separated.
Thanks to Tim Lyons for the suggestion.
(cherry picked from commit c11c63169f08495e8f03d7bb1aefc8ce5b3d6d5a)
