Fix some warnings from clang 10 in params.c

Fix some warnings from clang 10 in params.c

clang 10 was emitting warnings similar to the following from params.c:

crypto/params.c:411:40: error: implicit conversion from 'long' to 'double' changes value from 9223372036854775807 to 9223372036854775808 [-Werror,-Wimplicit-int-float-conversion]
            if (d >= INT64_MIN && d <= INT64_MAX && d == (int64_t)d) {

Also fixed some other conversion problems when sizeof(double) == 4.

Alternative to #13366

Fixes #13365

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/13377)