Document RAND_load_file change.

 Changes between 0.9.4 and 0.9.5  [xx XXX 1999]

  *) RAND_load_file(..., -1) reads the complete file and uses it to

     seed the PRNG (previously an explicit byte count was required).

     The bytes obtained by stat() are no longer counted for the

     return value.

     [Bodo Möller, Ulf Möller]

  *) Clean up CRYPTO_EX_DATA functions, some of these didn't have prototypes

     used (char *) instead of (void *) and had casts all over the place.

     [Steve Henson]