OCSP stapling: OCSP_basic_verify() OCSP_TRUSTOTHER flag now used.

This is expected to simplify configuration in a common case when OCSP
response is signed by a certificate already present in ssl_certificate
chain.  This case won't need any extra trusted certificates.

src/event/ngx_event_openssl_stapling.c

diff --git a/src/event/ngx_event_openssl_stapling.c b/src/event/ngx_event_openssl_stapling.c
index 435a40f..c09b9f7 100644
--- a/src/event/ngx_event_openssl_stapling.c
+++ b/src/event/ngx_event_openssl_stapling.c
@@ -588,7 +588,7 @@
     chain = staple->ssl_ctx->extra_certs;
 #endif
 
-    if (OCSP_basic_verify(basic, chain, store, 0) != 1) {
+    if (OCSP_basic_verify(basic, chain, store, OCSP_TRUSTOTHER) != 1) {
         ngx_ssl_error(NGX_LOG_ERR, ctx->log, 0,
                       "OCSP_basic_verify() failed");
         goto error;