Use Twin instead of std::to_string.

http://reviews.llvm.org/D14095

llvm-svn: 251365
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index d926f32..318b236 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3113,10 +3113,9 @@
     case bitc::IDENTIFICATION_CODE_EPOCH: { // EPOCH:      [epoch#]
       unsigned epoch = (unsigned)Record[0];
       if (epoch != bitc::BITCODE_CURRENT_EPOCH) {
-        auto BitcodeEpoch = std::to_string(epoch);
-        auto CurrentEpoch = std::to_string(bitc::BITCODE_CURRENT_EPOCH);
-        return error(Twine("Incompatible epoch: Bitcode '") + BitcodeEpoch +
-                     "' vs current: '" + CurrentEpoch + "'");
+        return error(
+          Twine("Incompatible epoch: Bitcode '") + Twine(epoch) +
+          "' vs current: '" + Twine(bitc::BITCODE_CURRENT_EPOCH) + "'");
       }
     }
     }