simplify mac address regex

let the computer do the counting and repetition and case

lib/puppet/parser/functions/is_mac_address.rb

@@ -15,7 +15,7 @@ Returns true if the string passed to this function is a valid mac address.
 
     mac = arguments[0]
 
-    if /^[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}$/.match(mac) then
+    if /^[a-f0-9]{1,2}(:[a-f0-9]{1,2}){5}$/i.match(mac) then
       return true
     else
       return false