fix memory allocation for auth_http_header

src/mail/ngx_mail_auth_http_module.c

diff --git a/src/mail/ngx_mail_auth_http_module.c b/src/mail/ngx_mail_auth_http_module.c
index 8028c95..c7e0fc0 100644
--- a/src/mail/ngx_mail_auth_http_module.c
+++ b/src/mail/ngx_mail_auth_http_module.c
@@ -1169,6 +1169,7 @@
                 + sizeof(CRLF) - 1
           + sizeof("Client-IP: ") - 1 + s->connection->addr_text.len
                 + sizeof(CRLF) - 1
+          + ahcf->header.len
           + sizeof(CRLF) - 1;
 
     b = ngx_create_temp_buf(pool, len);