[Mac] Fix SpinButton sizing and innner allocations
[Mac] Fix SpinButton sizing and innner allocations

The sizing and placement of the inner input field needs
to be done by the main container widget during the
ResizeSubviewsWithOldSize call while the main
widget has its final size.

mono/xwt,antmicro/xwt,lytico/xwt,TheBrainTech/xwt,hamekoz/xwt,hwthomas/xwt,cra0zy/xwt