Handling of special cases in EC arithmetic.
Removed test for point equality in ecdsa_verify_digest, point_add() already handles that.
Account for case when point.y == 0 when doubling.
Add required libraries to build on Linux
Add Makefile comments
Keep results after point_add() and point_double() inside the finite field. Simplified point_is_negative_of().
Removed superfluous bn_mod, it's done now in point_add and point_double.
Merge pull request #7 from hiviah/ecdsa_arithmetic_fix

Handling of special cases in ECDSA point arithmetic
Merge pull request #8 from dllaurence/linux-build

Linux build
Validating of public key curve point.
Tests for public key validity check.
Removed unnessary point copy.
Merge pull request #9 from hiviah/ecdsa_pubkey_validation

ECDSA public key validation
make pubkey validation optional, extract options to separate header
normalize y^2 in pubkey validation
fix last commit
rename BN_PRINT define to USE_BN_PRINT
use more warnings from trezor-mcu