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/serv.cpp

@@ -81,7 +81,7 @@ void main ()
 
   listen_sd = socket (AF_INET, SOCK_STREAM, 0);   CHK_ERR(listen_sd, "socket");
   
-  memset (&sa_serv, '\0', sizeof(sa_serv));
+  memset(&sa_serv, 0, sizeof(sa_serv));
   sa_serv.sin_family      = AF_INET;
   sa_serv.sin_addr.s_addr = INADDR_ANY;
   sa_serv.sin_port        = htons (1111);          /* Server Port number */