Test that SHA-1 defaults off

Added tests to validate that certificates signed using SHA-1 are
rejected by default, but accepted if SHA-1 is explicitly enabled.
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index e419ce9..9604b05 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -31,6 +31,14 @@
 	$(OPENSSL) x509 -req -extfile $(cli_crt_extensions_file) -extensions cli-rsa -CA test-ca-sha256.crt -CAkey $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -set_serial 4 -days 3653 -sha256 -in cli-rsa.csr -out $@
 all_final += cli-rsa-sha256.crt
 
+server2-rsa.csr: server2.key
+	$(OPENSSL) req -new -key server2.key -passin "pass:$(test_ca_pwd_rsa)" -subj "/C=NL/O=PolarSSL/CN=localhost" -out $@
+all_intermediate += server2-rsa.csr
+server2-sha256.crt: server2-rsa.csr
+	$(OPENSSL) x509 -req -extfile $(cli_crt_extensions_file) -extensions cli-rsa -CA test-ca-sha256.crt -CAkey $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -set_serial 4 -days 3653 -sha256 -in server2-rsa.csr -out $@
+all_final += server2-sha256.crt
+
+
 all_final: $(all_final)
 all: $(all_intermediate) $(all_final)