The encoding option was introduced in commit
270d909696a753af022df72a404c73f2895b4a02, to allow report callbacks to
format according to a given encoding. There was, however, no
connection between this encoding option, and the encoding of the
device to which the logger handler was writing.

Since a formatter is defined to return unicode:chardata(), and in
order to avoid mismatch with the encoding of the device, the encoding
option is now removed from the formatter. The handler itself must make
sure that it does not write illegal data to its device.

It can also return errors and warnings.

stdlib: Let dets:open_file() crash when given raw file name

See also https://bugs.erlang.org/browse/ERL-667.

See also ERL-55 and OTP-13229.

Consider the following functions:

    foo() -> bar(not_a_map).

    bar(M) when not is_map_key(a, M) -> ok;
    bar(_) -> error.

What will `foo/0` return? It depends. If the module is compiled
with the default compiler options, the return value will be
`ok`. If the module is compiled with the `inline` option,
the return value will be `error`.

The correct value is `error`, because the call to `is_map_key/2`
when the second argument is not a map should fail the entire
guard. That is the way other failing guards BIFs are handled.
For example:

    foo() -> bar(not_a_tuple).

    bar(T) when not element(1, T) -> ok;
    bar(_) -> error.

`foo/0` always returns `error` (whether the code is inlined
or not).

This bug can be fixed by changing the classification of `is_map_key/2`
in the `erl_internal` module. It is now classified as a type test,
which is incorrect because type tests should not fail. Reclassifying
it as a plain guard BIF corrects the bug.

This correction also fixes the internal consistency check
failure which was reported in:

https://bugs.erlang.org/browse/ERL-699

* siri/logger/post-21/OTP-15132:
  [logger] Allow setting kernel parameter 'logger_level' to 'all'
  [kernel] Reduce risk of dead lock when terminating logger_sup
  [logger] Fix regexp replacement for unicode strings
  Update proc_lib:report_cb to obey logger formatter's size limiting params
  [logger] Allow report callback with two arguments returning a string
  Don't call report_cb from cth_log_redirect - formatter does that
  Add legacy test of sasl_report_file_h and size limiting
  [logger] Remove compiler warnings in test
  [logger] Fix problem with test cases waiting for handler restart
  [logger] Add ?LOG macro which takes Level as argument
  [logger] Improve spec for set_handler_config/3 and set_primary_config/2
  [logger] Generate .png file from .dia
  [logger] Update documentation