Fix NSNotFound definition to use NSInteger type

[triplef]

Fixes #494.

I’m guessing this is an ABI breaking change, not sure how this should be handled.

[rfm]

To me this is a clear bug, which should be fixed asap. While it's technically an ABI change/break, I think in practice it will only cure problems, not break working code.

[triplef]

Sounds good. There was one test failure, because in NSCalendar.h we have another int enum:

enum
{
  NSDateComponentUndefined = NSIntegerMax,
  NSUndefinedDateComponent = NSDateComponentUndefined
};

I updated it to use NS_ENUM(NSInteger).

[triplef]

Any idea whether this failure on Windows MinGW GCC could be related?

base/NSRunLoop/thread.m:
Failed test:     (2025-03-17 16:08:02.762 GMT) thread.m:192 ... A loop with no inputs or timers will exit

[triplef]

The failure seems to have been intermittent. Still ok to merge with the additional changes @rfm?

[rfm]

The additional changes look ok to me.