Add a script to update copyright years

Now we just have to not forget to run it every year in January.

See https://github.com/wxWidgets/wxWidgets/pull/1302

misc/scripts/inc_year

@@ -0,0 +1,32 @@
+#!/bin/sh
+##############################################################################
+# Name:       misc/scripts/inc_year
+# Purpose:    increments the year in various copyright notices
+# Created:    2019-04-21
+# Copyright:  (c) 2019 Vadim Zeitlin <vadim@wxwindows.org>
+# Licence:    wxWindows licence
+##############################################################################
+
+. `dirname $0`/run_sed_common.sh
+
+new_year=`date +%Y`
+old_year=`expr $new_year - 1`
+
+echo "Updating dates to use $new_year instead of $old_year:"
+
+# Update copyright to extend to the new year.
+for f in CMakeLists.txt \
+         docs/doxygen/mainpages/copyright.h docs/doxygen/regen.sh \
+         interface/wx/aboutdlg.h interface/wx/generic/aboutdlgg.h \
+         ; do
+    run_sed $f "s/1992-$old_year/1992-$new_year/"
+done
+
+# Some files use later initial copyright year, for some reason...
+run_sed src/msw/version.rc "s/1993-$old_year/1993-$new_year/"
+run_sed src/common/utilscmn.cpp "s/1995-$old_year/1995-$new_year/"
+
+# And Mac files are much newer than that.
+for f in samples/docview/Info.plist samples/minimal/Info_cocoa.plist; do
+    run_sed $f "s/2005-$old_year/2005-$new_year/"
+done