Detect if the 'openssl' is really libressl at configure time.

Qt does not support libressl which reports itself as openssl but uses
a high version number. This means that we expect it to have features
that it doesn't and will fail to build. Instead detect this situation
at configure time and disable the ssl support.

Change-Id: I73cca4d1544df2aaca0723c38ba63758c287ec41
Reviewed-by: Ralf Nolden <nolden@kde.org>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@theqtcompany.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

config.tests/unix/openssl/openssl.cpp

@@ -37,6 +37,12 @@
 #  error "OpenSSL >= 0.9.7 is required"
 #endif
 
+#include <openssl/ssl.h>
+
+#if OPENSSL_VERSION_NUMBER-0 >= 0x10002000L && !defined(OPENSSL_NO_EC) && !defined(SSL_CTRL_SET_CURVES)
+#  error "OpenSSL was reported as >= 1.0.2 but is missing required features, possibly it's libressl which is unsupported"
+#endif
+
 int main()
 {
 }