Fix some compilation errors on msvc:
- "Redefinition of I" (iterator masks previous definition)
- include missing header file

Patch by Argiris Kirtzidis!

llvm-svn: 48115
diff --git a/llvm/lib/Transforms/IPO/ExtractGV.cpp b/llvm/lib/Transforms/IPO/ExtractGV.cpp
index a230dd1..882097c 100644
--- a/llvm/lib/Transforms/IPO/ExtractGV.cpp
+++ b/llvm/lib/Transforms/IPO/ExtractGV.cpp
@@ -17,6 +17,7 @@
 #include "llvm/Constants.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Support/Compiler.h"
+#include <algorithm>
 using namespace llvm;
 
 namespace {