script tests: add some new tests

These tests pass in bitcoind but currently fail in Haskoin.

Found with QuickCheck (see haskoin branch rpc-compare)
Script: fix OP_SIZE, boolean handling

test suite passes again, (seeming) parity with bitcoind
Script: use safer decodeInt

While bitcoind happily *encodes* integers into >4 bytes, it never *decodes*
anything that is >4 bytes. So script eval shouldn't have a function that does
that either.

The tests now also reflect these constraints.
script tests: add new test case

only last PUSHDATA byte was checked previously
script: fix decodeBool again

crazy that this can slip through

TODO: add test case
script tests: use better test case
script tests: fix test case for boolean constant
script: add test case testing popBool
script: fix popBool

also make order cases in OP_VERIFY more naturally
script: fix CHECKMULTISIG

TODO static tests
script tests: add tests for CHECKMULTISIG limits
Merge pull request #76 from OttoAllmendinger/fix-script

Fix script