Merge branch '2.3.0' into 2.4.0

Conflicts:
	AUTHORS
	CMakeLists.txt
	NEWS
	src/A3.cpp
	src/CMakeLists.txt
	src/Config.cpp
	src/Duration.cpp
	src/Duration.h
	src/Nibbler.cpp
	src/Nibbler.h
	src/RX.cpp
	src/RX.h
	src/columns/ColDate.cpp
	src/columns/ColScheduled.cpp
	src/commands/Command.cpp
	src/legacy.cpp
	src/utf8.cpp
	src/utf8.h
	test/CMakeLists.txt
	test/bug.mergedeps.t.postponed
	test/duration.t.cpp
	test/merge.duplicates.t
	test/merge.simple_duplication.t
	test/merge.t
	test/nibbler.t.cpp
	test/roundtrip.t
	test/rx.t.cpp
	test/utf8.t.cpp

test/rx.t.cpp

@@ -36,6 +36,10 @@ int main (int argc, char** argv)
 {
   UnitTest ut (23);
 
+  // Ensure environment has no influence.
+  unsetenv ("TASKDATA");
+  unsetenv ("TASKRC");
+
   std::string text = "This is a test.";
 
   RX r1 ("i. ", true);