Fix locations of shadowing warnings in ms_transform

A shadowed variable in an ms_transform match expression emits a warning
located at the match expression instead of the variable.
Fix miscompilation when module contains multiple named funs

A module containing two named funs bearing the same name and arity could be
miscompiled.

Reported-by: Sam Chapin
Remove comments about unicode atoms in OTP 18

There was once a plan to implement support for unicode atoms in OTP
18. This plan has been stopped until further notice, and the
information about this is now removed from the documentation.
Merge branch 'nox/compiler/eep37-duplicate-names/OTP-12262' into maint

* nox/compiler/eep37-duplicate-names/OTP-12262:
  Fix miscompilation when module contains multiple named funs
Merge branch 'nox/stdlib/ms_transform-locate-shadow-warning/OTP-12264' into maint

* nox/stdlib/ms_transform-locate-shadow-warning/OTP-12264:
  Fix locations of shadowing warnings in ms_transform
Merge branch 'siri/no-unicode-atoms/OTP-12172' into maint

* siri/no-unicode-atoms/OTP-12172:
  Remove comments about unicode atoms in OTP 18
erl_tar: Extend api to define own storage media access functions.

The reason for this is a requirement on enabling ssh_sftp to write a tar file on the server.
This new api function is used by ssh_sftp:open_tar/3,4.
ssh: Add ssh_sftp:open_tar/3,4 which opens a tar file at the server side of a channel.

Depends on erl_tar.erl having the function erl_tar:init/3 defined.
ssh: update vsn.mk
Merge branch 'hans/ssh/erl_tar_sftp/OTP-12180' into maint

* hans/ssh/erl_tar_sftp/OTP-12180:
  ssh: update vsn.mk
  ssh: Add ssh_sftp:open_tar/3,4 which opens a tar file at the server side of a channel.
  erl_tar: Extend api to define own storage media access functions.