On non-Windows, hard depend on uselocale(3)

[Tristan Partin]

I have been working on adding using thread-safe locale APIs within 
Postgres where appropriate[0]. The patch that I originally submitted 
crashed during initdb (whoops!), so I worked on fixing the crash, which 
led me to having to touch some code in chklocale.c, which became 
a frustrating experience because chklocale.c is compiled in 3 different 
configurations.

pgport_variants = {
  '_srv': internal_lib_args + {
    'dependencies': [backend_port_code],
  },
  '': default_lib_args + {
    'dependencies': [frontend_port_code],
  },
  '_shlib': default_lib_args + {
    'pic': true,
    'dependencies': [frontend_port_code],
  },
}

This means that some APIs I added or changed in pg_locale.c, can't be 
used without conditional compilation depending on what variant is being 
compiled. Additionally, I also have conditional compilation based on 
HAVE_USELOCALE and WIN32.

I would like to propose removing HAVE_USELOCALE, and just have WIN32, 
which means that Postgres would require uselocale(3) on anything that 
isn't WIN32.

[0]: https://www.postgresql.org/message-id/cwmw5ozbwj10.1yflqwsue5...@neon.tech

--
Tristan Partin
Neon (https://neon.tech)