Added define for STATUS_SUCCESS

Use STATUS_SUCCESS instead of 0.
Renamed USE_BCRYPT to RAND_WINDOWS_USE_BCRYPT to avoid possible collisions with other defines.
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1142)