Replace local mapl/2 (Erlang < 5.0) unique call by a LC
filelib:wildcard() should show broken symlinks

filelib:wildcard("broken_symlink") would return an empty list if
"broken_symlink" is a symlink that does not point to an existing
file.
Add default value for maps:get
Add docs and test for maps:get/3
stdlib: Fix error message when exporting (redefined) map() type

When redefining and exporting the type map() erl_lint erroneously
emitted an error. This bug has been fixed.
Update kernel, stdlib and sasl appup files for Erlang/OTP-18
Update kernel, stdlib and sasl appup tests

Add test of update instructions from current major to current
minor. Earlier only previous major to current was tested.
Remove the pg module and related documentation

This module has been marked experimental for more than 15 years,
and has largely been superseded by the pg2 module from the kernel
application. The original pg also has no tests and has not been
updated in the last 15 years other than small maintenance edits
(like adding specs or replacing pid/1 by is_pid/1). It is pretty
unlikely that anyone uses it today and its presence is simply
confusing as people should be using pg2 anyway.
Introduce the attribute -optional_callbacks in the context of behaviours
Allow more type names

product/_, union/_, range/2 as well as tuple/N (N > 0), map/N (N > 0),
atom/1, integer/1, binary/2, record/_, and 'fun'/_ can now be used as
type names.
Fix a -callback attribute bug

sys_pre_expand used to crash. There is no known reason to
allow -callback attributes with explicit module.
Disallow '_' as type variable

"... when _ :: ..." used to compile, but Dialyzer crashed.
Modify representation of the map type

Types are represented by quadruples {type, LINE, Name, Args},
but maps were represented by five-tuples
{type, LINE, map_field_assoc, Dom, Range}.

Note: this is *not* about the quadruples used for representing
expressions, {map_field_assoc,L,K,V}.
[stdlib] Simplify some linter warnings about specs

Use F/A rather than M:F/A for local functions.
Fix evaluation of map updates in the debugger and erl_eval

Reported-by: José Valim
Remove pre-defined types dict(), digraph(), &c

The pre-defined types array(), dict(), digraph(), gb_set(), gb_tree(),
queue(), set(), and tid() have been removed.
Merge branch 'essen/remove-pg'

* essen/remove-pg:
  Remove the pg module and related documentation

OTP-11907
Merge branch 'siri/appups-18.0/OTP-11881'

* siri/appups-18.0/OTP-11881:
  Update kernel, stdlib and sasl appup files for Erlang/OTP-18
Remove old code from stdlib/test/sys_sp2.erl

This code was related to an old implementation of sys:get_state and
sys:replace_state. sys_sp2.erl is now more like sys_sp1.erl - in order
to avoid confusion.
Merge branch 'bjorn/stdlib/file_lib-wildcard/OTP-11850' into maint

* bjorn/stdlib/file_lib-wildcard/OTP-11850:
  filelib:wildcard() should show broken symlinks