Doxygen: Reduce line gap in code fragments

Code should look compact, why use small fonts otherwise?
Reduce the gap between code lines (stored as separate <div>)
to 70%. This looks about right.

doc/img/edoxy.css

@@ -115,6 +115,7 @@ DIV.fragment {
 	padding-right: 2px;
 	padding-top: 2px;
 	padding-bottom: 2px;
+	line-height: 70%;
 }
 PRE.fragment {
         font-family: monospace, fixed;