Merge remote branch 'qatar/master'

* qatar/master:
  proto: include os_support.h in network.h
  matroskaenc: don't write an empty Cues element.
  lavc: add a FF_API_REQUEST_CHANNELS deprecation macro
  avio: move extern url_interrupt_cb declaration from avio.h to url.h
  avio: make av_register_protocol2 internal.
  avio: avio_ prefix for url_set_interrupt_cb.
  avio: AVIO_ prefixes for URL_ open flags.
  proto: introduce listen option in tcp
  doc: clarify configure features
  proto: factor ff_network_wait_fd and use it on udp

Conflicts:
	ffmpeg.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>