bug#27810: NS runtime feature detection

[Alan Third]

I wrote a big reply to this but seem to have lost it.

On Mon, Jul 24, 2017 at 09:02:57PM +0200, Charles A. Roelli wrote:
> nsterm.m: In function ‘-[EmacsView windowDidEnterFullScreen]’:
> nsterm.m:7395: error: ‘NSApplicationPresentationFullScreen’ undeclared
> (first use in this function)
> nsterm.m:7395: error: (Each undeclared identifier is reported only once
> nsterm.m:7395: error: for each function it appears in.)
> nsterm.m:7396: error: ‘NSApplicationPresentationAutoHideToolbar’ undeclared
> (first use in this function)

I think perhaps we need to just test ‘< 10.7’. I’ve attached a new
patch that deals with that and some other bits and pieces.

> I'm confused why the macro call you wrote doesn't prevent this. But
> when I change it to #if MAC_OS_X_VERSION_MIN_ALLOWED <=
> MAC_OS_X_VERSION_10_6, then it compiles.  This min/max stuff always
> confuses me...

I’m unclear where we should be using MIN_REQUIRED vs MAX_ALLOWED, but
I think we’re OK with MAX everywhere for what we’re doing. I’ve just
used MAX in both my new macros.

We need a proper runtime OS version check in a few places. I think
there are two ways of doing this depending on which OS version you’re
building on. It’s getting very close to circular. ;)

macfont.m looks like it could be a small nightmare as it has a LOT of
version dependent code.

Thanks for testing this patch.
-- 
Alan Third

0001-Use-a-run-time-check-for-macOS-Sierra-tabbing-suppor.patch
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