Add a DiffShowEditor showing an additional info

Task-number: QTCREATORBUG-9489

Change-Id: I3ae2e59ccaf397f4236505f21e027a42e2798784
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Petar Perisin <petar.perisin@gmail.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/plugins/coreplugin/core.qrc

@@ -36,6 +36,7 @@
         <file>images/replace.png</file>
         <file>images/reset.png</file>
         <file>images/sidebaricon.png</file>
+        <file>images/topbaricon.png</file>
         <file>images/splitbutton_horizontal.png</file>
         <file>images/statusbar.png</file>
         <file>images/undo.png</file>

src/plugins/coreplugin/coreconstants.h

@@ -194,6 +194,7 @@ const char ICON_CLEAR[]              = ":/core/images/clear.png";
 const char ICON_RESET[]              = ":/core/images/reset.png";
 const char ICON_MAGNIFIER[]          = ":/core/images/magnifier.png";
 const char ICON_TOGGLE_SIDEBAR[]     = ":/core/images/sidebaricon.png";
+const char ICON_TOGGLE_TOPBAR[]      = ":/core/images/topbaricon.png";
 const char ICON_CLOSE_DOCUMENT[]     = ":/core/images/button_close.png";
 const char ICON_CLOSE[]              = ":/core/images/closebutton.png";
 const char ICON_CLOSE_DARK[]         = ":/core/images/darkclosebutton.png";