Prevent detection of libressl as openssl >= 1.1

--- qtbase/config.tests/unix/openssl11/openssl.cpp	2017-11-30 14:49:46.000000000 +0100
+++ qtbase/config.tests/unix/openssl11/openssl.cpp	2018-01-27 18:01:17.206523715 +0100
@@ -39,7 +39,7 @@
 
 #include <openssl/opensslv.h>
 
-#if !defined(OPENSSL_VERSION_NUMBER) || OPENSSL_VERSION_NUMBER-0 < 0x10100000L
+#if !defined(OPENSSL_VERSION_NUMBER) || defined(LIBRESSL_VERSION_NUMBER) || (OPENSSL_VERSION_NUMBER-0 < 0x10100000L)
 #  error "OpenSSL >= 1.1 is required"
 #endif