Update README.md
Merge pull request #108

6c7f0c6 Update README.md (Pieter Wuille)
Add DETERMINISTIC to avoid line number/source dependent binaries

This will make it easier to detect changes without semantic impact.
Merge pull request #107

f49b2ef Add DETERMINISTIC to avoid line number/source dependent binaries (Pieter Wuille)
Make secp256k1_eckey_pubkey_serialize fail for infinity
Test whether recovered public keys are not infinity

Fixes a bug discovered by Sergio Demian Lerner.
Add test that recovering infinity fails
Merge pull request #110

3bf029d Add test that recovering infinity fails (Pieter Wuille)
4861f83 Test whether recovered public keys are not infinity (Pieter Wuille)
bbe67d8 Make secp256k1_eckey_pubkey_serialize fail for infinity (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