Add SM9 demos

demos/sm9/sm9_keygen_demo.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <gmssl/sm9.h>
+
+
+int main(void)
+{
+	SM9_SIGN_MASTER_KEY sign_master;
+	SM9_SIGN_KEY sign_key;
+
+	sm9_sign_master_key_generate(&sign_master);
+
+	printf("SM9 Master Secret\n");
+	sm9_sign_master_key_info_encrypt_to_pem(&sign_master, "P@ssw0rd", stdout);
+
+	printf("SM9 Public Parameters\n");
+	sm9_sign_master_public_key_to_pem(&sign_master, stdout);
+
+	sm9_sign_master_key_extract_key(&sign_master, "alice", strlen("alice"), &sign_key);
+
+	printf("SM9 private key for ID '%s'\n", "alice");
+	sm9_sign_key_info_encrypt_to_pem(&sign_key, "123456", stdout);
+
+	return 0;
+}