wx: Add missing wxTextCtrl:changeValue

It was missing.
wx: Add wxActivateEvent
erts: Fix various autoconf issues

* Check of atomics on bsd
* Add --enable-systemd for epmd
* Remove unused --enable-tsp option
wx: Fix non constant define (wxSL_LABELS)

wxSL_LABELS have changed constant value in 3.0, make version agnostic
by doing a lookup during runtime instead of constant.

Thanks Enrique Fernández (efcasado)
wx: Add wxPopup(Transient)Window

Useful class though not documented in wxWidgets-2.8
Fix permissions of some files in the repository

These files aren't supposed to be executable. For reference, the command used to
find them was:

	git ls-files -z | xargs -0 -J % find % -type f -perm ++x
wx: Fix destroy bug

Do not postpone deletion of wx*DC objects since they need to be
deleted directly. Otherwise, if inside showModal, causes an eternal
loop of wxPaint events on Windows.
Merge branch 'dgud/wx/additional-functionality/OTP-11986' into maint

* dgud/wx/additional-functionality/OTP-11986:
  wx: Fix destroy bug
  wx: Add wxPopup(Transient)Window
  wx: Fix non constant define (wxSL_LABELS)
  wx: Add wxActivateEvent
  wx: Add missing wxTextCtrl:changeValue

OTP-11985
Prepare release