stop ./configure at once on library failure

auto/lib/openssl/conf

@@ -66,6 +66,17 @@ else
                 have=NGX_SSL . auto/have
                 CORE_LIBS="$CORE_LIBS $ngx_feature_libs $NGX_LIBDL"
                 OPENSSL=YES
+            else
+
+cat << END
+
+$0: error: SSL modules require the OpenSSL library.
+You can either do not enable the modules, or install the OpenSSL library
+into the system, or build the OpenSSL library statically from the source
+with nginx by using --with-openssl=<path> option.
+
+END
+                exit 1
             fi
         ;;