FS-9612 #resolve [RTCP-MUX wrongly enabled in cases where answer contains rtcp but offer didn't / remote addr not obtained in UDPTL mode] %backport=1.6

FS-9601: mod_opus:  make adjustable bitrate mutually exclusive with FEC enforcing on the decreasing trend,
add step calculation for bitrate adjustment, fix bug on context settings

FS-8644: OPUS_SET_BITRATE(), codec control and estimators for packet loss and RTT (with Kalman filters) to detect a slow or congested link.
Feature enabled with "adjust-bitrate" in opus.conf.xml - it's a feedback loop with incoming RTCP.

Merge pull request #969 in FS/freeswitch from ~DRAGOS_OANCEA/freeswitch-dragos:fix_config_rtpip to master

* commit '3d2f3c96':
  FS-9548: return with error on wrong rtp ip given from config

* commit 'c70f06aa':
  FS-9553 #resolve [Refactor video-on-hold]

* commit '5e323ee9':
  newest version of sleep patch
  FS-8623: reapply after update: Fix libvpx Solaris Studio build
  FS-8623: reapply after update: fix sun studio build errors building libvpx
  update to libvpx b46243d from repo https://chromium.googlesource.com/webm/libvpx

Merge pull request #968 in FS/freeswitch from ~DINGDING/freeswitch:bugfix/FS-9536-fix-switch_core_hash_delete-return-invalid to master

* commit '9f01830d':
  FS-9536 [core] fix return value