Unbreak build with gcc 4.3: provide missed includes and silence most annoying warnings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47367 91177308-0d34-0410-b5e6-96231b3b80d8

lib/ExecutionEngine/ExecutionEngine.cpp

@@ -26,7 +26,8 @@
 #include "llvm/System/DynamicLibrary.h"
 #include "llvm/System/Host.h"
 #include "llvm/Target/TargetData.h"
-#include <math.h>
+#include <cmath>
+#include <cstring>
 using namespace llvm;
 
 STATISTIC(NumInitBytes, "Number of bytes of global vars initialized");