[CF] Unify common locale macros.

[3405691582]

Linux (except Android or Cygwin) and Windows don't support extended
locales, so a number of preprocessor macros are in Prefix to default to
the standard API that uses the C locale. Both Linux and Windows have
some macros in common and some platform specialized definitions; here,
we split out the common macros and keep the platform-specific
definitions separate.

This will let us more simply extend support for different platforms that
also don't support extended locales in a future commit.

[compnerd]

I think that this is incorrect. It is in fact the opposite I believe. Linux but not android supports the extended locale variant. Windows does not. I'm not certain about cygwin, but I imagine that it does as well. It just Android (below a certain version per interface) and Windows which do not support the extended locales.

[3405691582]

I think I was confused with the earlier PR. Adjusted the commit description to describe what CF is doing rather than what is the state of the world.

The code change is -- in a mechanical sense -- still OK since the macros aren't more specially controlled than TARGET_OS_LINUX.

I'm not sure off the top of my head what the state of locale support is on Linux. CF however thinks Linux doesn't have extended locale APIs, but maybe that's changed. I can look at that later.

(Of course, this is confused by the fact that Android supports xlocale.h, these macros are defined unconditionally for Android because Android is TARGET_OS_LINUX, and then those macros become irrelevant anyway when xlocale.h is #included elsewhere in CFInternal.h. And indeed Cygwin probably supports xlocale.h but in CFInternal.h is prevented from being #include'd, so maybe it didn't in the past?)

[compnerd]

I think I was confused with the earlier PR. Adjusted the commit description to describe what CF is doing rather than what is the state of the world.

Thanks.

The code change is -- in a mechanical sense -- still OK since the macros aren't more specially controlled than TARGET_OS_LINUX.

Agreed.

I'm not sure off the top of my head what the state of locale support is on Linux. CF however thinks Linux doesn't have extended locale APIs, but maybe that's changed. I can look at that later.

Could you please? That would be a great improvement.

[compnerd]

@swift-ci please test

[3405691582]

Could you please? That would be a great improvement.

Certainly. I'm not very familiar with a lot of the locale stuff, but a cursory look suggests most of the invocations pass NULL for a locale, which uses the C locale default. Nevertheless, there looks like some potential for some cleanup.