[archive_acl] Reject ACL entries with out-of-range numeric IDs

[archive_acl] Reject ACL entries with out-of-range numeric IDs

isint() and isint_w() previously clamped values >= INT_MAX to INT_MAX
and returned success, allowing malformed ACL text to silently set IDs
to an arbitrary sentinel value.  Change them to return -1 (a new
"overflow" indication) instead, and update all callers in both the
NFS4 and POSIX parsers (narrow and wide) to treat overflow as
ARCHIVE_WARN and skip the offending entry.

Add test_acl_nfs4_text.c with four test functions covering NFS4 ACL
text round-trips, audit/alarm entry types, numeric-ID handling
including the overflow boundary (INT_MAX - 1 accepted, INT_MAX
rejected), and malformed-entry error paths.