[mythtv] fixing macOS compilation...

[David Hampton]

On Mon, 2018-10-15 at 20:38 +0200, Piotr Oniszczuk wrote:
> David,
> 
> FYI: 
> I played a little with current master to get it compiling on current
> macOS (mojave).
> Attached patch allows me to compile current master. 
> pls look at it rather as pointers where code needs to be fixed - not
> as optimised changes…

Hmm, that's reverting the changes I made converting the code base over
to use the new C++11 nullptr value.  I tried running a few of those
variable types down in the Apple developer documentation I could find,
and it looks like all the values in the first two files are pointers of
some sort and therefore should use nullptr.  That said, what happens if
you use zeros in darwinavcinfo.h and darwinfirewiredevice.cpp instead
of nullptr/NULL?

The third file definitely should be returning 0 instead of NULL or
nullptr.  The return value of CGDirectDisplayID is alised to an UInt32.

David