Add tool tip to the file name tabs

[Daniel J Sebald]

Torsten,

I see you were just working on the file name in the GUI/IDE editor tabs. 
 Please consider adding this patch

https://savannah.gnu.org/patch/index.php?7933

that sets a tool tip to the full-length file name if the file name is 
all that is displayed.  With that, there is the option to have condensed 
names in the tabs (i.e., more tabs visible) yet get the full path name 
via an easy move of the cursor.

Thanks,

Dan