Make lb302 include math.h so we can switch it to C++11

M_PI is no longer defined by default in C++11, but lb302.cpp needs it.
Therefore, before switching to C++11, we add an include.

plugins/lb302/lb302.cpp

@@ -28,6 +28,10 @@
  *
  */
 
+// Need to include this first to ensure we get M_PI in MinGW with C++11
+#define _USE_MATH_DEFINES
+#include <math.h>
+
 #include "lb302.h"
 #include "AutomatableButton.h"
 #include "Engine.h"