Make SendEvent callable from all threads

This commit refactors the SendEvent call and moves it from the Input
ReaderBackend to to MsgThread. This allows all other types of threads
to access this functionality.

This necessitated a few more changes. Most importantly, one of the
ValueToVal methods was moved over to SerialTypes. Whereit arguably
belongs - there was nothing that was input-framework specific in
that method - and the functionality could come in useful in a number
of cases.

src/threading/BasicThread.h

@@ -37,7 +37,7 @@ public:
 
 	/**
 	 * Returns a descriptive name for the thread. If not set via
-	 * SetName(). If not set, a default name is choosen automatically.
+	 * SetName(), a default name is chosen automatically.
 	 *
 	 * This method is safe to call from any thread.
 	 */