Various simplifications of the code:

+ use a wrapper around ast_carefulwrite(), used in two places,
  to make life easier when we decide to use a different interface
  to the socket.

+ put an ast_verbose() message on astman_append on a case that
  should never happen now that we use a temporary file for
  AMI-over-HTTP sessions

+ document and slightly simplify process_events() by removing
  unnecessary parentheses.

+ in get_input(), use ast_wait_for_input() instead of poll().

  We may want to move to a completely non-blocking


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@48080 65c4cc65-6c06-0410-ace0-fbb531ad65f3