Improve ecrecover tests

[axic]

The negative tests seem to be mostly concerned by checking dirty bits for the v value, but there aren't many trying out various 1-byte values. On example was discussed under #941.

The goal would be to include cases with v values 0, 1, 2, 3, 29, 30 and a bunch of other random values, plus potentially those used with chainid based signing.

stPreCompiledContracts2/CALLCODEEcrecoverV_prefixedf0Filler could be used to easily extend this test suite.

(See also ethereum/yellowpaper#860)

[winsvega]

we have more transaction signature tests here
https://github.com/ethereum/tests/tree/develop/src/TransactionTestsFiller

have you run it?

[axic]

I see these tests were added in #1080, but they seem to be enabled on >=London only. Any reason for that? They should be enabled since Frontier, because the ecrecover precompile never changed.

[axic]

we have more transaction signature tests here
https://github.com/ethereum/tests/tree/develop/src/TransactionTestsFiller

@winsvega Sorry for the late response, the tests cases I was missing are not transaction encoding, but ecrecover precompile. @qbzzt did those tests however.