honour client min window size

[Antoine Martin]

windows with a title bar have a minimum size on win32, we should tell the server to honour it so that when an application requests a size smaller than that we will send the configure-notify event with the min-size applied to it.

[Antoine Martin]

Mostly done in r20851, minor fixups in r20854. Test in r20855.

max-size and the new min-size switch can be used on either the client or server (previously max-size was only used by the client)

Still TODO:

• also apply it for OR windows? (force XConfigureWindow?)
• use it with the desktop server to restrict randr resizing
• man page

[Antoine Martin]

As of r20949, the min-size only applies to decorated windows, undecorated windows don't have any min-size restrictions.
r20950: max-size applies to all windows.

[Antoine Martin]

Updates:

• r20991 improve test
• r20992 remove unused code
• r20993 + r20994: decorations flag may not be set, in which case the window IS decorated

More to come, including a fix for size constraints validation (done on the values after we already copied them... doh)

[Antoine Martin]

Implementation complete in r20996 (+ man page in r20997).

Still TODO: backport fix.

[Antoine Martin]

Backport in r21001.

Not doing the desktop server randr limitation or applying it to OR windows.

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/1969