useful for script to be able to alert setbg that something has changed. For
example, a script named rmbg might look at ~/.setbg to get the name of the
current background image file and remove it then signal setbg with SIGUSR1 to
-have it re-evaluate the state of bgdirs.
+have it re-evaluate the state of bgdirs.
Finally setbg will perform the this re-evaluation at midnight everyday. This is
-useful because we point setbg to look at -bgdirs from Dropbox where Camera
+useful because we point setbg to look at -bgdirs from Dropbox where Camera
Uploads is included and new pictures can arrive everyday.
=cut