Make sure we handle a uint32_t payload in ast_frdup()

(closes issue #14080)
Reported by: fnordian
Patches:
      frame.patch uploaded by fnordian (license 110)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@164519 65c4cc65-6c06-0410-ace0-fbb531ad65f3