Update release documentation files for 3.1.4

Change version number and update the list of changes.

docs/publicity/announce.txt

@@ -1,8 +1,8 @@
-October 28, 2019 -- The wxWidgets team is pleased to announce a new
+July 22, 2020 -- The wxWidgets team is pleased to announce a new
 release of our open source framework for the development of native
 cross-platform applications in C++.
 
-wxWidgets 3.1.3 is the latest release in the 3.1 development
+wxWidgets 3.1.4 is the latest release in the 3.1 development
 branch and is now available at
 
     https://www.wxwidgets.org/downloads/
@@ -10,39 +10,37 @@ branch and is now available at
 Compared to the stable 3.0.x series, this version brings many
 improvements and even more bug fixes, please see the change log
 
-https://raw.githubusercontent.com/wxWidgets/wxWidgets/v3.1.3/docs/changes.txt
+https://raw.githubusercontent.com/wxWidgets/wxWidgets/v3.1.4/docs/changes.txt
 
 for the incomplete list of the most important ones. Here is the
 maximally condensed summary of the changes compared to 3.0:
 
-- Build system improvements: support for new compilers (up to MSVS 2019, g++ 9)
+- Build system improvements: support for new compilers (up to MSVS 2019, g++ 10)
   with an even simpler way of using wxWidgets from MSVS, with wxwidgets.props
   file, and OS versions as well as an entirely new CMake build system.
-- Support for native dark mode under macOS 10.14 Mojave and later.
+- Support for native dark mode under macOS 10.14 Mojave and later and support
+  for macOS 11 on ARM hardware.
 - New features: implement freezing rows/columns in wxGrid; support for mouse
   gesture events (GSoC 2017 project); non-integer font sizes and arbitrary font
   weights in wxFont; fractional pen widths in wxGraphicsContext; arbitrary
   label windows in wxStaticBox; markup in wxDataViewCtrl items text; better
   support for high DPI monitors and per-monitor DPI and dynamic DPI changes
   support under MSW; support for ZIP 64 files; LZMA compression; much improved
-  accessibility support under MSW.
+  accessibility support under MSW; new Edge-based wxWebView implementation.
 - New classes: wxActivityIndicator, wxAddRemoveCtrl,
   wxAppProgressIndicator, wxNativeWindow, wxPowerResourceBlocker,
-  wxSecretStore.
-- And methods: wxDataViewToggleRenderer::ShowAsRadio(), wxDateTime::
-  GetWeekBasedYear(), wxDisplay::GetPPI(), wxGrid::SetCornerLabelValue(),
-  wxHtmlEasyPrinting::SetPromptMode(), wxJoystickEvent::GetButtonOrdinal(),
-  wxListBox::GetTopItem(), wxProcess::Activate(), wxTextEntry::ForceUpper(),
-  several ones in wxRendererNative, wxStandardPaths::GetUserDir(),
-  wxToolbook::EnablePage(), wxUIActionSimulator::Select() and many others.
-- New XRC handlers for wxActivityIndicator, wxAui classes, wxDataViewCtrl,
-  wxInfoBar, wxSimplebook, wxSpinCtrlDouble.
-- Significant improvements to: wxBusyInfo, wxDataViewCtrl,
-  wxNotificationMessage, wxStaticBox, wxStyledTextCtrl.
+  wxSecretStore, wxTempFFile and many new features in the existing classes.
+- New XRC handlers for all the new and some of the existing classes.
+- Significant improvements to: wxBusyInfo, wxDataViewCtrl, wxDirDialog, wxGrid,
+  wxNotificationMessage, wxSpinCtrl, wxStaticBox, wxStyledTextCtrl,
+  wxUIActionSimulator.
+- Improvements to compile-time safety with the possibility to disable dangerous
+  implicit conversions between wxString and "char*" strings.
 - Latest versions of all bundled 3rd party libraries, including all the
   security fixed and support for WebKit 2 and GStreamer 1.7 under Unix.
 - Revamped OpenGL support better suited to modern OpenGL (3.2+).
-- Further C++11 support improvements.
+- Further C++11 and later support improvements, wxWidgets can be built using
+  C++20 compilers.
 - A lot of bug fixes, especially in wxGTK3 and wxOSX/Cocoa ports.
 - New experimental wxQt port.