Codechange: Replace custom thread code with C++11 thread objects.

We assume a conforming C++11 compiler environment that has a valid <thread>-header.
Failure to run a real thread is handled gracefully.

src/os/os2/os2.cpp

@@ -18,6 +18,7 @@
 #include "../../core/random_func.hpp"
 #include "../../string_func.h"
 #include "../../textbuf_gui.h"
+#include "../../thread.h"
 
 #include "table/strings.h"
 
@@ -226,3 +227,7 @@ void OSOpenBrowser(const char *url)
 	// stub only
 	DEBUG(misc, 0, "Failed to open url: %s", url);
 }
+
+void SetCurrentThreadName(const char *)
+{
+}