move the declaration of struct ast_channel ast_frame and ast_module

to compat.h so it is always available - hopefully this will let
us reduce the number of inclusions of channel.h and frame.h



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@89426 65c4cc65-6c06-0410-ace0-fbb531ad65f3