Add test cases for AES OFB block mode

Adds test cases from NIST SP800-38A for OFB block mode to AES-128/192/256, for
the configuration of MBEDTLS_CIPHER_MODE_OFB.
diff --git a/tests/Makefile b/tests/Makefile
index d85617f..e15d945 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -46,7 +46,8 @@
 endif
 
 APPS =	test_suite_aes.ecb$(EXEXT)	test_suite_aes.cbc$(EXEXT)	\
-	test_suite_aes.cfb$(EXEXT)	test_suite_aes.rest$(EXEXT)	\
+	test_suite_aes.cfb$(EXEXT)		test_suite_aes.ofb$(EXEXT)	\
+	test_suite_aes.rest$(EXEXT)	\
 	test_suite_arc4$(EXEXT)		test_suite_asn1write$(EXEXT)	\
 	test_suite_base64$(EXEXT)	test_suite_blowfish$(EXEXT)	\
 	test_suite_camellia$(EXEXT)	test_suite_ccm$(EXEXT)		\
@@ -109,6 +110,10 @@
 	echo "  Gen   $@"
 	perl scripts/generate_code.pl suites test_suite_aes test_suite_aes.cfb
 
+test_suite_aes.ofb.c : suites/test_suite_aes.function suites/test_suite_aes.ofb.data scripts/generate_code.pl suites/helpers.function suites/main_test.function
+	echo "  Gen   $@"
+	perl scripts/generate_code.pl suites test_suite_aes test_suite_aes.ofb
+
 test_suite_aes.rest.c : suites/test_suite_aes.function suites/test_suite_aes.rest.data scripts/generate_code.pl suites/helpers.function suites/main_test.function
 	echo "  Gen   $@"
 	perl scripts/generate_code.pl suites test_suite_aes test_suite_aes.rest
@@ -209,6 +214,10 @@
 	echo "  CC    $<"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) $<	$(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
 
+test_suite_aes.ofb$(EXEXT): test_suite_aes.ofb.c $(DEP)
+	echo "  CC    $<"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) $<	$(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
+
 test_suite_aes.rest$(EXEXT): test_suite_aes.rest.c $(DEP)
 	echo "  CC    $<"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) $<	$(LOCAL_LDFLAGS) $(LDFLAGS) -o $@