Take a stab at OTP 18 compatability with macro logging

Handle yet another stacktrace form

Sometimes the stacktrace is a larger array of {M, F, A, Prop} tuples.
The handler code was expecting at most 2 tuples in the list. Relax this
requirement and add a test that provokes this edge-case.

support logging with macros per level

Dont flush notify msgs at overload

add reverse_pretty_stacktrace env var, default true

Handle OTP 20 gen_server crash when the client pid is dead

Support unicode format string

A little emphasis on application variable crash_log

Emphasize application variable

Added info about application place holder.

Support for dynamic metadata

Fix the bug with the wrong format.

Make the high water mark shaper better

Enable sending console output to standard error

* If the shaper is in overload and the final message comes in, but no
  further messages arrive for some time, until another message came in,
  the drop count would not be printed. Now we set a timer to ensure it
  prints the drop count after the current second expires.
* Allow the shaper to take a filter function that allows events that
  would not normally be printed anyway to not be counted against the
  HWM. This means that if you're suppressing supervisor startup messages
  you won't see drop events counted for messages you'd never see
  printed.

Fixes for OTP 20

* Handle new gen_server crash messages that contain client pid and stacktrace
* Update platform define for OTP 20
* Handle arity change in gen_fsm handle_msg