xclip-set: Set both clipboard & primary

I always try to use shift+Insert in terminals, so I want the password in
the primary selection as well.

I realize not everybody wants this,
mattydebie#32 for example is
proposing a workflow of copying username into one selection, and
password into another.

bwmenu

@@ -284,7 +284,7 @@ clipboard-clear() {
 }
 
 clipboard-xclip-set() {
-    xclip -selection clipboard -r
+    xclip -selection clipboard -r -f | xclip -selection primary -r
 }
 
 clipboard-xclip-get() {