Fix abi.decint

[janx]

abi.decint is used to decode BOTH signed and unsigned integers.

Problem

• it make the bound check hard to understand, because it mixes int's lower bound and uint's upper bound:
  if is_numeric(n) and n < 2**256 and n >= -2**255:
• If the input is bytes it will always decode those bytes to unsigned int, cause inconsistent semantic - if input is int/uint, the output is int/uint; if input is bytes of int/uint, the output is uint.

Fix

Add a new argument signed, default to False, behave accordingly.

Consequence

With signed int's bound check fix, test_ecrecover breaks because the types of its arguments default to int256. Declare them to uint256.

$ cat test_ecrecover.se

def test_ecrecover(h, v, r, s):
    return(ecrecover(h, v, r, s))

$ serpent mk_signature test_ecrecover.se

extern test_ecrecover.se: [test_ecrecover:[int256,int256,int256,int256]:int256]

[coveralls]

Changes Unknown when pulling a1e604d on janx:fix_abi_decint into * on ethereum:develop*.

[ulope]

Merged. Thanks for the fix :)