Add a space between literal and string macro to eliminate warning under G++.

compile_commands.json

@@ -74,11 +74,6 @@
   "command": "/usr/bin/c++  -DBOOST_ASIO_NO_DEPRECATED -DWEBCC_ENABLE_LOG -DWEBCC_ENABLE_SOAP -DWEBCC_LOG_LEVEL=0 -I/usr/local/include -I/home/adam/github/webcc -I/home/adam/github/webcc/third_party/src    -std=c++11 -o CMakeFiles/webcc.dir/rest_async_client.cc.o -c /home/adam/github/webcc/webcc/rest_async_client.cc",
   "file": "/home/adam/github/webcc/webcc/rest_async_client.cc"
 },
-{
-  "directory": "/home/adam/github/webcc/build/webcc",
-  "command": "/usr/bin/c++   -DBOOST_ASIO_NO_DEPRECATED -DWEBCC_ENABLE_LOG -DWEBCC_ENABLE_SOAP -DWEBCC_LOG_LEVEL=0 -I/usr/local/include -I/home/adam/github/webcc -I/home/adam/github/webcc/third_party/src    -std=c++11 -o CMakeFiles/webcc.dir/rest_client.cc.o -c /home/adam/github/webcc/webcc/rest_client.cc",
-  "file": "/home/adam/github/webcc/webcc/rest_client.cc"
-},
 {
   "directory": "/home/adam/github/webcc/build/webcc",
   "command": "/usr/bin/c++  -DBOOST_ASIO_NO_DEPRECATED -DWEBCC_ENABLE_LOG -DWEBCC_ENABLE_SOAP -DWEBCC_LOG_LEVEL=0 -I/usr/local/include -I/home/adam/github/webcc -I/home/adam/github/webcc/third_party/src    -std=c++11 -o CMakeFiles/webcc.dir/rest_request_handler.cc.o -c /home/adam/github/webcc/webcc/rest_request_handler.cc",

webcc/http_request.cc

@@ -15,7 +15,8 @@ void HttpRequest::Make() {
     SetHeader(kHost, host_ + ":" + port_);
   }
 
-  SetHeader(kUserAgent, "Webcc/"WEBCC_VERSION);
+  // NOTE: C++11 requires a space between literal and string macro.
+  SetHeader(kUserAgent, "Webcc/" WEBCC_VERSION);
 }
 
 }  // namespace webcc