Travis CI: Try to get OpenSSL 1.1 from an alternative source

.travis.yml

@@ -732,9 +732,11 @@ matrix:
     addons:
       apt:
         sources:
-          - ubuntu-toolchain-r-test
+          - sourceline: 'ppa:ondrej/nginx-mainline'
         packages:
           - libssl1.1
+          - openssl
+          - libssl-dev
     env:
       idx=20
       N=GCCLinuxDefault_OpenSSL11

src/civetweb.c

@@ -12846,6 +12846,7 @@ is_websocket_protocol(const struct mg_connection *conn)
 		           * fields
 		           */
 	}
+	DEBUG_TRACE("Upgrade: %s", upgrade);
 	if (!mg_strcasestr(upgrade, "websocket")) {
 		return 0;
 	}