ssl: fix compile error with OpenSSL 1.0.0

OpenSSL <= 1.0.0 did not support TLS 1.1/1.2, and thus we must still
check the existence of the symbols. This fixes the previous commit,
3e5a009 ("ssl: remove unsupported TLS versions from
SSLContext::METHODS", 2017-08-08).

Author: rhenium

ext/openssl/extconf.rb

@@ -113,6 +113,8 @@ def find_openssl_library
 # like OPENSSL_NO_SSL2 may not be defined.
 have_func("SSLv2_method")
 have_func("SSLv3_method")
+have_func("TLSv1_1_method")
+have_func("TLSv1_2_method")
 have_func("RAND_egd")
 engines = %w{builtin_engines openbsd_dev_crypto dynamic 4758cca aep atalla chil
              cswift nuron sureware ubsec padlock capi gmp gost cryptodev aesni}

ext/openssl/ossl_ssl.c

@@ -74,10 +74,10 @@ static const struct {
 #if !defined(OPENSSL_NO_TLS1) && !defined(OPENSSL_NO_TLS1_METHOD)
     OSSL_SSL_METHOD_ENTRY(TLSv1, TLS1_VERSION),
 #endif
-#if !defined(OPENSSL_NO_TLS1_1) && !defined(OPENSSL_NO_TLS1_1_METHOD)
+#if !defined(OPENSSL_NO_TLS1_1) && !defined(OPENSSL_NO_TLS1_1_METHOD) && defined(HAVE_TLSV1_1_METHOD)
     OSSL_SSL_METHOD_ENTRY(TLSv1_1, TLS1_1_VERSION),
 #endif
-#if !defined(OPENSSL_NO_TLS1_2) && !defined(OPENSSL_NO_TLS1_2_METHOD)
+#if !defined(OPENSSL_NO_TLS1_2) && !defined(OPENSSL_NO_TLS1_2_METHOD) && defined(HAVE_TLSV1_2_METHOD)
     OSSL_SSL_METHOD_ENTRY(TLSv1_2, TLS1_2_VERSION),
 #endif
     OSSL_SSL_METHOD_ENTRY(SSLv23, 0),