Core: fixed segfault with null in wildcard hash names. A configuration like server { server_name .foo^@; } server { server_name .foo; } resulted in a segmentation fault during construction of server names hash. Reported by Markus Linnala. Found with afl-fuzz.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  0
#endif

END