make local variables local

.. to not interfere with variables in the scripts that source these utils.

mailer.sh

@@ -2,12 +2,12 @@
 
 mailer () {
 if ! [[ -z "$3" ]]; then
-    mailfrom="From: $3 <christian@betz.cc>"
+    local mailfrom="From: $3 <christian@betz.cc>"
 fi
 if ! [[ -z "$4" ]]; then
-    mailto="$4"
+    local mailto="$4"
 elif [[ -z "$mailto" ]]; then
-    mailto="christian@betz.cc"
+    local mailto="christian@betz.cc"
 fi
 
 echo -e "$1" | mailx -s "$2" --append="$mailfrom" $mailto &>/dev/null