(cherry picked from commit 98ce8fd8)

Fix FIR wrongly formatted according to RFC 5104

Fix issue where feedback packets gets queued and exceed the MAX_IOV, causing the RTCP packet to be truncated.
Fix an issue where some feedback RTCP packets could be sent immediately but were not.

This option makes the creation of 'package_source' custom target optional,
allowing to build with CMake < 3.11 if it is disabled (default).

(cherry picked from commit a64eecad)

Reformat CHANGELOG and adapt CMakeLists.txt

fix(rtp): avoid false-positive overflow detected by UBSan with timestamp macros

See merge request !1

(cherry picked from commit e06fccea)

add more precise check on std atomic, specialy to avoid using uncompatible implementatiwqon (gcc 4.9 android)