Introduce hints to ABI_FILE to select fat binary entries

[kevemueller]

With this change ABI_FILE accepts an optional suffix separated by '#' from the path, this suffix is an architecture description, the same format as ALTABI after :.

The architecture hint is used to select a matching architecture from a Mach-O universal binary file.

Extend the pkg_abi_macho to use the provided architecture (hint) to select the right binary from an universal binary.
Add unit tests for this use case.
Also improve error handling and remove a memory leak.

[kevemueller]

Closes #2345

NB: If there is no hint provided, I have opted to continue to select the first entry. Emitting a notice here breaks many unit tests, so I do this silently.
Putting together the 'native' ALTABI string seemed a big overhead and is in general against the new philosophy that it should not matter where you run pkg.

[kevemueller]

Sorry for the multi-force push, there was a last minute code-formatter introduced include re-ordering as well as the obvious -o IGNORE_OSMAJOR=1 needed on FreeBSD.

[kevemueller]

This is now merged to reflect your changes with ABI and ALTABI.
Based on those changes I guess I need to rewrite this to use ABI (3rd, TARGET_ARCH entry) as the selector and not ALTABI (3rd &4th entry, a.k.a ELF architecture) which I use right now.
Please confirm and I will do the small change.

[bapt]

I confirm

[kevemueller]

Using now ABI, logic remains the same.
Added multiple ATF-checks for all sort of corner cases.
The shlibs parsing remains empty. I will write that after the new shlibs is implemented with ELF.

[bapt]

I have introduce another conflict which I hope I have properly fixed before merging this.