Re: AIX support

Thanks for your continued push for AIX support! Here are a few comments:

> # The static libpq is skipped in AIX. This is not required.

For comments like this, I would generally like to see some links or 
inline documentation to why this is the case. Maybe Peter or Heikki 
disagree.

There are a few places in the Meson code like the following:

	if AIX:
		don't define the static library target
	endif

Make sure that the innards of the if statements are indented. 
Alternatively, you could define something like:

	static_library_dependencies = []
	if host_machine.system() == 'AIX'
		# TODO: Document this
		AIX_poison_pill = disabler()
		static_library_dependencies += AIX_poison_pill
	endif

And then for all static library definitions, you would just make sure 
that they all depend on the poison pill. You could document the AIX 
shared/static library situation where the AIX_poison_pill variable is 
defined. I'd like to see if Peter thinks this is a good idea before 
implementing it.

I'm also a little confused by the second patch. Some of it seems to be 
the same, and some other parts seem to be new. Should we consolidate all 
Meson AIX support into one patch? Overall, I think the size of the patch 
is good, and seem pretty maintainable.

-- 
Tristan Partin
Databricks (https://databricks.com)