Revert "Introduce a string_ostream string builder facilty"

Temporarily back out commits r211749, r211752 and r211754.

llvm-svn: 211814
diff --git a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
index 35e4a56..9151d99 100644
--- a/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
+++ b/llvm/lib/CodeGen/MachineBlockFrequencyInfo.cpp
@@ -89,9 +89,10 @@
 
   std::string getNodeLabel(const MachineBasicBlock *Node,
                            const MachineBlockFrequencyInfo *Graph) {
-    string_ostream OS;
+    std::string Result;
+    raw_string_ostream OS(Result);
 
-    OS << Node->getName() << ":";
+    OS << Node->getName().str() << ":";
     switch (ViewMachineBlockFreqPropagationDAG) {
     case GVDT_Fraction:
       Graph->printBlockFreq(OS, Node);
@@ -104,7 +105,7 @@
                        "never reach this point.");
     }
 
-    return OS.str();
+    return Result;
   }
 };