Enable system locale - change from the standard (C) to system locale.

[josch]

This allows libarchive (in case it is activated) to handle filenames.
We only change LC_CTYPE since libarchive only needs the charset set.
We don't use LC_ALL because it causes problems on some systems.
We restore the original LC_CTYPE after extraction to avoid side effects.
We use uselocale instead of setlocale to avoid setting LC_CTYPE globally.
See on libarchive Website for a more complete description of the issue:
libarchive/libarchive#587
https://github.com/libarchive/libarchive/wiki/Filenames
https://github.com/sbabic/swupdate/blob/master/handlers/archive_handler.c#L94

[josch]

Without it, handling a tarball in pax format containing utf8 characters in its filenames will result in this error message:

archive_read_next_header(): Pathname can't be converted from UTF-8 to current locale.