* raimo/receive-TOS-TCLASS/ERIERL-187/OTP-15145:
  Write testcases for recvtos and friends
  Fix term buffer overflow bug
  Fix documentation due to feedback
  Implement socket option recvtos and friends

* john/erts/improve-list-reverse-trapping/OTP-15199:
  Improve trapping in lists:reverse/2
  Fix unsafe use of lists:reverse/1

* rickard/conf-pgo/OTP-15282:
  Fix PGO configure test

* hasse/syntax_tools/fix_revert/OTP-15294:
  erts: Add comment about [] and nil() to The Abstract Format
  syntax_tools: Correct erl_syntax:revert/1

If the process had more free space than reductions it could run a
lot longer than it was supposed to. It didn't honor the number of
reductions going in either, nor did it bump reductions when
returning its result or erroring out.

This commit also removes this function from a work function in
scheduler_SUITE as it's extremely sensitive to the number of
reductions spent in the test, causing
equal_and_high_with_part_time_max to fail on some machines.

We said reverse/2 but used reverse/1 which is unsafe to use in
preloaded modules. This didn't have any effect in practice as the
affected functions weren't used before the code server was started,
but it's still an error.

* maint-21:
  Updated OTP version
  Update release notes
  Update version numbers
  erts: Fix "Prevent inconsistent node lists" fix
  Fix include-path regression caused by dd0a39c
  Restore default SIGTERM behaviour for port programs