changes to make it compatible with 64bit gcc

llvm-svn: 2792
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 98de447..99ee45e 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -25,6 +25,7 @@
 #include "Support/STLExtras.h"
 #include "Support/StatisticReporter.h"
 #include <algorithm>
+using std::string;
 
 static Statistic<> NumHoistedNPH("licm\t\t- Number of insts hoisted to multiple"
                                  " loop preds (bad, no loop pre-header)");