memset, memcpy, sizeof consistency fixes

Just as with the OPENSSL_malloc calls, consistently use sizeof(*ptr)
for memset and memcpy.  Remove needless casts for those functions.
For memset, replace alternative forms of zero with 0.

Reviewed-by: Richard Levitte <levitte@openssl.org>

demos/ssl/cli.cpp

@@ -47,7 +47,7 @@ void main ()
   
   sd = socket (AF_INET, SOCK_STREAM, 0);       CHK_ERR(sd, "socket");
  
-  memset (&sa, '\0', sizeof(sa));
+  memset(&sa, 0, sizeof(sa));
   sa.sin_family      = AF_INET;
   sa.sin_addr.s_addr = inet_addr ("127.0.0.1");   /* Server IP */
   sa.sin_port        = htons     (1111);          /* Server Port number */