libroot/crypt: replace crypt_des implementation with musl's

This is required to make crypt_r() really reentrant.

Change-Id: I81497be16cae21fabb5895a88e27e6c20d3e06e0
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6066
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>