THRIFT-177. cpp: Add a missing "std::"


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@706418 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/Thrift.cpp b/lib/cpp/src/Thrift.cpp
index c784015..fb6bcbc 100644
--- a/lib/cpp/src/Thrift.cpp
+++ b/lib/cpp/src/Thrift.cpp
@@ -54,7 +54,7 @@
 
 std::string TOutput::strerror_s(int errno_copy) {
 #ifndef HAVE_STRERROR_R
-  return "errno = " + boost::lexical_cast<string>(errno_copy);
+  return "errno = " + boost::lexical_cast<std::string>(errno_copy);
 #else  // HAVE_STRERROR_R
 
   char b_errbuf[1024] = { '\0' };