Revert "Introduce a string_ostream string builder facilty"

Temporarily back out commits r211749, r211752 and r211754.

llvm-svn: 211814
diff --git a/llvm/utils/FileCheck/FileCheck.cpp b/llvm/utils/FileCheck/FileCheck.cpp
index 2c33e68..978e05f 100644
--- a/llvm/utils/FileCheck/FileCheck.cpp
+++ b/llvm/utils/FileCheck/FileCheck.cpp
@@ -458,7 +458,8 @@
   // variable values.
   if (!VariableUses.empty()) {
     for (unsigned i = 0, e = VariableUses.size(); i != e; ++i) {
-      small_string_ostream<256> OS;
+      SmallString<256> Msg;
+      raw_svector_ostream OS(Msg);
       StringRef Var = VariableUses[i].first;
       if (Var[0] == '@') {
         std::string Value;