skin_engine: Clean up %x() handling - beware theme issues

Internally remove some hacks around how %x() is handled.
%x() inside the default viewport will no longer work if
other viewports are used, so if you are using viewports and
%x() make sure it is in a viewport!

Change-Id: I8ecab805d55fc0f8476ff0516cba38e23400aa20

wps/cabbiev2.112x64x1.wps

@@ -5,6 +5,7 @@
 %wd
 #
 # Load Backdrop
+%V(0,0,-,-,-)
 %x(z,wpsbackdrop-112x64x1.bmp,0,0)
 #
 # Preload Images

wps/cabbiev2.128x64x1.wps

@@ -11,12 +11,11 @@
 %xl(D,shuffle-128x64x1.bmp,0,1)
 %xl(E,repeat-128x64x1.bmp,0,0,4)
 %xl(F,playmode-128x64x1.bmp,0,0,5)
-%x(a,pbbackground-128x64x1.bmp,1,0)
 %xl(b,bar-128x64x1.bmp,2,0)
 #
 # Progress Bar
 %V(0,0,128,6,1)
-#%xd(a)
+%x(a,pbbackground-128x64x1.bmp,1,0)
 %pb(2,1,123,4,pb-128x64x1.bmp)
 #
 # Separator Bar