Add missing standard headers. Patch by Joerg Sonnenberger!

llvm-svn: 122193
diff --git a/llvm/lib/Target/SubtargetFeature.cpp b/llvm/lib/Target/SubtargetFeature.cpp
index ba53d63..3cf95b5 100644
--- a/llvm/lib/Target/SubtargetFeature.cpp
+++ b/llvm/lib/Target/SubtargetFeature.cpp
@@ -18,6 +18,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cctype>
+#include <cstdlib>
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//