Dav: added error logging. Previously, when request body was not available or was previously read in memory rather than a file, client received HTTP 500 error, but no explanation was logged in error log. This could happen, for example, if request body was read or discarded prior to error_page redirect, or if mirroring was enabled along with dav.

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


cat << END >> $NGX_AUTO_HEADERS_H

#ifndef $have
#define $have  1
#endif

END