cleaned up Curl_write() and the sub functions it uses for various protocols.

They all now return ssize_t to Curl_write().

Unfortunately, Curl_read() is in a sorrier state but it too would benefit from
a similar cleanup.

lib/security.c

@@ -278,6 +278,13 @@ Curl_sec_write(struct connectdata *conn, int fd, char *buffer, int length)
   return tx;
 }
 
+ssize_t
+Curl_sec_send(struct connectdata *conn, int num, char *buffer, int length)
+{
+  curl_socket_t fd = conn->sock[num];
+  return (ssize_t)Curl_sec_write(conn, fd, buffer, length);
+}
+
 int
 Curl_sec_putc(struct connectdata *conn, int c, FILE *F)
 {