Switch scalar to use get/set 32-byte arrays
Add unit tests for scalars.

Also add a secp256k1_scalar_is_one function.
Merge pull request #76

7935930 Add unit tests for scalars. (Pieter Wuille)
eca6cdb Switch scalar to use get/set 32-byte arrays (Pieter Wuille)
Add bench_inv tool
Remove OpenSSL bignum implementation
Merge pull request #78

520ba3c Remove OpenSSL bignum implementation (Pieter Wuille)
Merge pull request #79

ae2679b Add bench_inv tool (Pieter Wuille)
Make bench deterministic
Rename bench to bench_verify
Merge pull request #80

504c63d Rename bench to bench_verify (Pieter Wuille)
01097dd Make bench deterministic (Pieter Wuille)
Avoid division when decomposing scalars

- In secp256k1_gej_split_exp, there are two divisions used. Since the denominator is a constant known at compile-time, each can be replaced by a multiplication followed by a right-shift (and rounding).
- Add the constants g1, g2 for this purpose and rewrite secp256k1_gej_split_exp accordingly.
- Remove secp256k1_num_div since no longer used