fixup! [tree] Small cleanups in TEventList.

Author: hageboeck

tree/tree/src/TEventList.cxx

@@ -50,6 +50,7 @@ the TEventList object created in the above commands:
 #include "TBuffer.h"
 #include "TCut.h"
 #include "TDirectory.h"
+#include "TMathBase.h"
 
 ////////////////////////////////////////////////////////////////////////////////
 /// Create a EventList.