Thomas Bushnell's patch to protect non-backup pruning (#164875).

[Derek Atkins]

Log Message:
-----------
Thomas Bushnell's patch to protect non-backup pruning (#164875).

	* src/backend/file/gnc-backend-file.c:
	  When working on the file foo.xac, backups are named
	  foo.DATE.xac.  But the backup file pruner will prune any old
	  file named foo.DATE.anything.

Tags:
----
gnucash-1-8-branch

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/backend/file:
        gnc-backend-file.c