Thrift string copy construction pathces from kevin ko

Summary: Remove unnecessary string copy constructions in C++ code

Reviewed By: mcslee

Test Plan: build


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665084 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/protocol/TProtocolException.h b/lib/cpp/src/protocol/TProtocolException.h
index ba2fbfb..8f939c6 100644
--- a/lib/cpp/src/protocol/TProtocolException.h
+++ b/lib/cpp/src/protocol/TProtocolException.h
@@ -42,11 +42,11 @@
     facebook::thrift::TException(), 
     type_(type) {}
 
-  TProtocolException(const std::string message) :
+  TProtocolException(const std::string& message) :
     facebook::thrift::TException(message),
     type_(UNKNOWN) {}
 
-  TProtocolException(TProtocolExceptionType type, const std::string message) :
+  TProtocolException(TProtocolExceptionType type, const std::string& message) :
     facebook::thrift::TException(message),
     type_(type) {}