unistd: Increase maximum passwd/group buffer to 1MB

We have one UNIX group that contains most of our users whose size is
about 20 kB, so `Group::from_name` is failing with ERANGE.

The discussion on PR #864 suggests that 1 MB is a reasonable maximum -
it follows what FreeBSD's libc does. (glibc appears to have no maximum
on the _r function and will just double the buffer until malloc fails,
but that's not particularly Rusty.)

0 files changed, 0 insertions, 0 deletions