win32: Handle all window changes in WINDOWPOSCHANGED
win32: Handle all window changes in WINDOWPOSCHANGED

This moves all the code from WM_SIZE, WM_MOVE, and WM_SHOWWINDOW into
one place, cleans up the code and makes sure we only send a single
configure event even if both size and position changes.

grubersjoe/adwaita,davidgumberg/gtk,jessevdk/gtk,grubersjoe/adwaita,davidt/gtk,Distrotech/gtk2,Adamovskiy/gtk,ahodesuka/gtk,grubersjoe/adwaita,jessevdk/gtk,ebassi/gtk,jigpu/gtk,Lyude/gtk-,Sidnioulz/SandboxGtk,davidgumberg/gtk,jadahl/gtk,jadahl/gtk,grubersjoe/adwaita,chergert/gtk,jigpu/gtk,ahodesuka/gtk,davidt/gtk,msteinert/gtk,bratsche/gtk-,alexlarsson/gtk,Sidnioulz/SandboxGtk,chergert/gtk,Sidnioulz/SandboxGtk,Lyude/gtk-,chergert/gtk,chergert/gtk,Distrotech/gtk2,jadahl/gtk,ahodesuka/gtk,alexlarsson/gtk,jessevdk/gtk,bratsche/gtk-,Lyude/gtk-,jadahl/gtk,Adamovskiy/gtk,alexlarsson/gtk,jessevdk/gtk,Lyude/gtk-,jadahl/gtk,jigpu/gtk,Adamovskiy/gtk,jessevdk/gtk,msteinert/gtk,chergert/gtk,msteinert/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,ahodesuka/gtk,Adamovskiy/gtk,alexlarsson/gtk,msteinert/gtk,chergert/gtk,bratsche/gtk-,ahodesuka/gtk,davidgumberg/gtk,ahodesuka/gtk,Distrotech/gtk2,alexlarsson/gtk,jadahl/gtk,jigpu/gtk,jessevdk/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,ahodesuka/gtk,Adamovskiy/gtk,ebassi/gtk,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,ebassi/gtk,davidgumberg/gtk,davidgumberg/gtk,jadahl/gtk,davidt/gtk,Distrotech/gtk2,Distrotech/gtk2,Lyude/gtk-,jigpu/gtk,ebassi/gtk,davidt/gtk,msteinert/gtk,bratsche/gtk-,Adamovskiy/gtk,davidt/gtk,Adamovskiy/gtk,jigpu/gtk,ebassi/gtk,davidt/gtk,alexlarsson/gtk,Lyude/gtk-,chergert/gtk,ahodesuka/gtk,ebassi/gtk,bratsche/gtk-,Lyude/gtk-,Sidnioulz/SandboxGtk,Distrotech/gtk2,jigpu/gtk,Lyude/gtk-,jadahl/gtk,davidgumberg/gtk,jigpu/gtk,davidgumberg/gtk,Sidnioulz/SandboxGtk,grubersjoe/adwaita,davidgumberg/gtk,jessevdk/gtk,bratsche/gtk-,msteinert/gtk