Add test for issue #104.

tests/issue-104-unreferenced-periodic-timer.d

@@ -0,0 +1,23 @@
+/+ dub.sdl:
+	name "test"
+	dependency "vibe-core" path=".."
++/
+module test;
+
+import vibe.core.core;
+
+import core.memory;
+import core.time;
+
+
+int main()
+{
+	setTimer(10.seconds, { assert(false, "Event loop didn't exit in time."); });
+
+	// make sure that periodic timers for which no explicit reference is stored
+	// are still getting invoked periodically
+	size_t i = 0;
+	setTimer(50.msecs, { if (i++ == 3) exitEventLoop(); }, true);
+
+	return runEventLoop();
+}