Missing strtof_l strtod_l strtold_l calls

[mmu_man]

When trying to update the OpenColorIO port it failed to build because we miss ​those locale-aware calls. Seems they are on Linux too but without manpages, and likely non-POSIX.

[waddlesplash]

musl appears to ignore the "locale" argument and just calls the non _l versions of these functions.

We're still on the glibc versions of strtof/strtod/strtold, though. I think when I looked at switching us to musl's versions, we would need to import parts of the musl stdio as well, and I didn't want to pull that trigger. But perhaps it's time to do that, and we can see about keeping glibc's stdio (for compatibility).

[pulkomandy]

If these are nonstandard, I think it's better to not implement them at all rather than imhlementing them in a way that doesn't work as expected?