So we stop duplicating the code if we try to improve it later on :D

close #2089

skins2 manages a cache for building layouts. Yet, on each redraw/expose,
it rebuilds the whole layout. This patch avoids these unnecessary rebuilds.
It results in dramatic improvement, especially on Linux, where refresh was a real issue.

On X11, windows are created with a 1x1 size and updated later on.
In some context, vout_display can catch this 1x1 size before the size is updated.
This results in a crash in swcaler.c which gets a 1x0 size (division by zero)
Changing default to 10x10 solves the problem.

Revert "Win32: fix #2592 (stdin file input). It may impact other platforms, so please test, and fix/revert if you see a bug."

This reverts commit e33a82db.
This broke opening any file starting with a dash.

This enables passing a below state in addition to currently supported
always-on-top (above) and normal. (However, none of the window provider
support it just yet).

Should fix aspect-ratio issues and fixes #2793

Win32: fix #2592 (stdin file input). It may impact other platforms, so please test, and fix/revert if you see a bug.