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/.gitignore b/tests/data_files/.gitignore
index 7611e9b..d16c04c 100644
--- a/tests/data_files/.gitignore
+++ b/tests/data_files/.gitignore
@@ -1,2 +1,3 @@
 cli-rsa.csr
+server2-rsa.csr
 test-ca.csr
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)
 
diff --git a/tests/data_files/server2-sha256.crt b/tests/data_files/server2-sha256.crt
new file mode 100644
index 0000000..006d9db
--- /dev/null
+++ b/tests/data_files/server2-sha256.crt
@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----