Add some missing includes for the build against stdcxx.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161657 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 33bc1c9..c68d62b 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -49,6 +49,7 @@
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Target/TargetOptions.h"
 #include <bitset>
+#include <cctype>
 using namespace llvm;
 
 STATISTIC(NumTailCalls, "Number of tail calls");