Specify UTF-8 charset when forming data from plain text

This suppresses a browser warning about unspecified character encoding
of an HTTP response.

src/base/http/types.h

@@ -63,7 +63,7 @@ namespace Http
 
     const char CONTENT_TYPE_HTML[] = "text/html";
     const char CONTENT_TYPE_CSS[] = "text/css";
-    const char CONTENT_TYPE_TXT[] = "text/plain";
+    const char CONTENT_TYPE_TXT[] = "text/plain; charset=UTF-8";
     const char CONTENT_TYPE_JS[] = "application/javascript";
     const char CONTENT_TYPE_JSON[] = "application/json";
     const char CONTENT_TYPE_GIF[] = "image/gif";

src/webui/api/torrentscontroller.cpp

@@ -601,9 +601,9 @@ void TorrentsController::addAction()
     }
 
     if (partialSuccess)
-        setResult("Ok.");
+        setResult(QLatin1String("Ok."));
     else
-        setResult("Fails.");
+        setResult(QLatin1String("Fails."));
 }
 
 void TorrentsController::addTrackersAction()