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)
Rewrite mul/sqr for 32bit/64bit

- interleave calculation of the lower and upper partial product ranges, and reduction
- less registers needed, more opportunities for parallel ops