OCSP stapling: fixed segfault without nextUpdate.
OCSP stapling: fixed segfault without nextUpdate.

OCSP responses may contain no nextUpdate.  As per RFC 6960, this means
that nextUpdate checks should be bypassed.  Handle this gracefully by
using NGX_MAX_TIME_T_VALUE as "valid" in such a case.

The problem was introduced by 6893a1007a7c (1.9.2).

Reported by Matthew Baldwin.

hy0kl/nginx,hy0kl/nginx,hy0kl/nginx