Changed every memcpy to SCA equivalent mbedtls_platform_memcpy

This makes physical attacks more difficult.
diff --git a/library/ssl_cache.c b/library/ssl_cache.c
index 7d376f7..a4d8cd3 100644
--- a/library/ssl_cache.c
+++ b/library/ssl_cache.c
@@ -290,7 +290,7 @@
             goto exit;
         }
 
-        memcpy( cur->peer_cert.p,
+        mbedtls_platform_memcpy( cur->peer_cert.p,
                 cur->session.peer_cert->raw.p,
                 cur->session.peer_cert->raw.len );
         cur->peer_cert.len = session->peer_cert->raw.len;