Integrate BIL validation into test framework

[tim-becker]

The changes in https://github.com/tim-becker/qira/tree/concrete_execution add a concrete executor for the BAP IL to QIRA. Although initially meant to find bugs in BAP's lifter, the validation actually revealed subtle bugs in QIRA as well (see PR #93 and PR #87). So, it seems like this code could be useful for regression testing as well.

@geohot @nedwill , thoughts?

[geohot]

Support!