Updated the sha1 for saga-gis to be the actual sha1 listed on SorceForge

The current sha1 hash in the saga-gis formula is incorrect.  See the [SourceForge repository](http://sourceforge.net/projects/saga-gis/files/SAGA%20-%202.1/SAGA%202.1.1/).

I was consistently getting a "bad download" until I made this change.