Make greentext pickier

> must be the first character (i.e. leading whitespace disables greentext)
> must be followed by a "word" character, with an optional space (sorry zetok, but this is much more intuitive)
> followed by two+ spaces doesn't count
Fixes #945

src/widget/tool/chatactions/messageaction.cpp

@@ -63,7 +63,7 @@ QString MessageAction::getMessage(QString div)
     message_ = "";
     for (QString& s : messageLines)
     {
-        if (QRegExp("^[ ]*>.*").exactMatch(s))
+        if (QRegExp("^> ?\\w.*").exactMatch(s))
             message_ += "<span class=quote>" + s + "</span><br/>";
         else
             message_ += s + "<br/>";