Common C type definitions

To better indicate their use and ensure code portability, some common C types have been redefined.

Typedef     char                    aat_ascii;
Typedef     unsigned char           aat_byte;
Typedef     short int               aat_int16;
Typedef     long int                aat_int32;
Typedef     unsigned short int      aat_uint16;
Typedef     unsigned long int       aat_word32;
Typedef     short int               aat_bool;
enum        aat_bool
{
  aat_false False=0,
  aat_true True=1
};