We only use this
1. if we have localeconv_l
2. to get the decimal point / thousands separator for numbers
So we can ignore all this and directly create a purely LC_NUMERIC locale.
This *was* more useful when we were in C++ and the printing functions
all relied on locale, but we only use this in printf and that only
extracts the number stuff.
* Fix build on NetBSD
Notably:
1. A typo in `f_flag` vs `f_flags` - this was probably never tested
2. Some pointless name differences - `st_mtimensec` vs
`st_mtime_nsec`
3. The big one: This said that LC_GLOBAL_LOCALE() was -1 "everywhere".
Well, not on NetBSD.
* ifdef for macos
I had originally created a safe `set_locale()` wrapper and clippy-disallowed
`libc::setlocale()` but almost all our uses of `libc::setlocale()` are in a loop
where it makes much more sense to just obtain the lock outright then call
`setlocale()` repeatedly rather than lock it in the wrapper function each time.
