rtpproxy: update to current snapshot

rtpproxy: update to current snapshot

Upstream accepted OpenWrt patches, so most can be removed.

Other changes:

- version handling changed to use PKG_SOURCE_DATE and PKG_SOURCE_VERSION
  as per OpenWrt package policies [1]
- ./files/rtpproxy.config renamed to ./files/rtpproxy.conf also as per
  OpenWrt package policies [1]
- no longer needed Makefile variables dropped (PKG_SOURCE_SUBDIR etc.)
- PKG_CHECK_FORMAT_SECURITY:=0 dropped, patch for that upstreamed as
  well
- PKG_BUILD_PARALLEL:=1 added
- PKG_LICENSE_FILES updated
- dropped bcg729 deactivation hack (fixed by adding bcg729 pkg-config
  file in other commit)
- dependency on libatomic now required
- updated rtpproxy-mod-acct-csv TITLE
- added --without-xsltproc to CONFIGURE_ARGS to prevent build failure
- added new module rtpproxy-mod-acct-rtcp-hep
- added utilities extractaudio and makeann
- updated patch to prevent debug build of rtpp_acct_rtcp_hep

[1] https://openwrt.org/docs/guide-developer/package-policies

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>