because we're only handling words anyway) in BN_mod_exp_mont_word
making it a little faster for very small exponents,
and adjust the performance gain estimate in CHANGES according
to slightly more thorough measurements.
(15% faster than BN_mod_exp_mont for "large" base,
20% faster than BN_mod_exp_mont for small base.)
but the BN code had some problems that would cause failures when
doing certificate verification and some other functions.
Submitted by: Eric A Young from a C2Net version of SSLeay
Reviewed by: Mark J Cox
PR: