* mpi/mpih-const-time.c (_gcry_mpih_set_cond): Replace single mask + XOR
with dual mask + AND/OR; Add comment about reason for dual mask usage.
(_gcry_mpih_add_n_cond, _gcry_mpih_sub_n_cond, _gcry_mpih_swap_cond)
(_gcry_mpih_abs_cond): Add comment about reason for dual mask usage.