[ENHANCEMENT] Add new PE_HeaderSectionMenu primitive element

This is needed to make the PopupMenuTitle UI element work properly

src/kernel/qstyle.h

@@ -223,6 +223,8 @@ public:
 	PE_PanelGroupBox,
 	PE_RubberBand,
 
+	PE_HeaderSectionMenu,
+
 	// do not add any values below/greater this
 	PE_CustomBase =			0xf000000
     };

src/styles/qcommonstyle.cpp

@@ -283,6 +283,7 @@ void QCommonStyle::drawPrimitive( PrimitiveElement pe,
     case PE_ButtonTool:
     case PE_ButtonDropDown:
     case PE_HeaderSection:
+    case PE_HeaderSectionMenu:
 	qDrawShadePanel(p, r, cg, flags & (Style_Sunken | Style_Down | Style_On) , 1,
 			&cg.brush(QColorGroup::Button));
 	break;