Mercurial: Work on Windows using Tortoise Hg, polishing.

Do not use "cmd /c hg" on Windows as this will fail randomly
depending on arguments with blanks, such as "-U 8". Output log
messages about synchronous commands, format author correctly,
label menus correctly.

src/plugins/mercurial/mercurialplugin.h

@@ -83,6 +83,7 @@ public:
     QString currentProjectName();
     QFileInfo currentProjectRoot();
     bool closeEditor(Core::IEditor *editor);
+    QStringList standardArguments() const;
 
     MercurialSettings *settings();