Change the defacto output transform from flipped-270 to flipped-90

It turns out that flipped-270 is the second-simplest transformation besides
normal because it is a direct swapping of the x and y axes.  Having that as
the default encourages people to use flipped-270 as the default test for "I
want to try this with a transform".  Unfortunately, because flipped-270 is
so simple, it is really easy to have something that works for normal,
flipped-270, and nothing else.  This encourages people to test with a
transform thats actually "hard".

weston.ini.in

@@ -59,7 +59,7 @@ path=@libexecdir@/weston-keyboard
 #[output]
 #name=X1
 #mode=1024x768
-#transform=flipped-270
+#transform=flipped-90
 
 #[touchpad]
 #constant_accel_factor = 50