Fix uiAreaBeginUserWindowResize on macOS

[mischnic]

• CGFLOAT_MAX isn't a valid value for a constraint

• The position (= origin) of the window changes when resizing on the left or bottom edge and needs to be adjusted while resizing.

Fixes #357

[mischnic]

libui/darwin/winmoveresize.m

Lines 111 to 119 in cda991b

	// maximum: encourage the window to be as large as possible
	contentView = [w contentView];
	cw = uiprivMkConstraint(contentView, NSLayoutAttributeWidth,
	NSLayoutRelationEqual,
	nil, NSLayoutAttributeNotAnAttribute,
	0, CGFLOAT_MAX,
	@"window maximum width finding constraint");
	[cw setPriority:NSLayoutPriorityDragThatCanResizeWindow];
	[contentView addConstraint:cw];

Is there a case where a window with an uiArea can't grow infinitely large? There are no "non-stretchy" uiArea with a fixed size.

[andlabs]

Not yet, but there will be.

[mischnic]

Could it (a max width/height) somehow occur with another control in the window?

So is 100000 as maximum contraint width/height fine for now, because there is no SOMETHING_MAX value that works?

[andlabs]

The fact there is no such constant is the reason why I was using CGFLOAT_MAX. I suppose I could make 100000 a constant, but I still wonder why this fails now on Sierra.

[mischnic]

The largest possible value that works (High Sierra) is 4294967384.0, which is UINT_MAX + 89.

[mischnic]

What keeps this from getting merged? Even if this might not be a perfect solution (although there seems to be no case in which the maximum size constraint has any effect) , it's still better than the application crashing.