feat(ssl): Restructure ssl folder

Put mbedtls, axtls, openssl to ssl, also add kconfig to choose ssl library.
Default use mbedtls.

components/ssl/openssl/include/internal/ssl_pkey.h

@@ -0,0 +1,86 @@
+// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef _SSL_PKEY_H_
+#define _SSL_PKEY_H_
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+#include "ssl_types.h"
+
+/**
+ * @brief create a private key object according to input private key
+ *
+ * @param ipk - input private key point
+ *
+ * @return new private key object point
+ */
+EVP_PKEY* __EVP_PKEY_new(EVP_PKEY *ipk);
+
+/**
+ * @brief create a private key object
+ *
+ * @param none
+ *
+ * @return private key object point
+ */
+EVP_PKEY* EVP_PKEY_new(void);
+
+/**
+ * @brief load a character key context into system context. If '*a' is pointed to the
+ *        private key, then load key into it. Or create a new private key object
+ *
+ * @param type   - private key type
+ * @param a      - a point pointed to a private key point
+ * @param pp     - a point pointed to the key context memory point
+ * @param length - key bytes
+ *
+ * @return private key object point
+ */
+EVP_PKEY* d2i_PrivateKey(int type,
+                         EVP_PKEY **a,
+                         const unsigned char **pp,
+                         long length);
+
+/**
+ * @brief free a private key object
+ *
+ * @param pkey - private key object point
+ *
+ * @return none
+ */
+void EVP_PKEY_free(EVP_PKEY *x);
+
+/**
+ * @brief load private key into the SSL
+ *
+ * @param type - private key type
+ * @param ssl  - SSL point
+ * @param len  - data bytes
+ * @param d    - data point
+ *
+ * @return result
+ *     0 : failed
+ *     1 : OK 
+ */
+ int SSL_use_PrivateKey_ASN1(int type, SSL *ssl, const unsigned char *d, long len);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif