Do not unnecessary follow tag types when storing the boolbv mapping

[tautschnig]

Types in equations must match exactly, there is no need to follow tags
when checking for type consistency. Also, do not use a followed type
when storing the mapping. When retrieving a mapped value, assert type
consistency.

This is a bugfix, but apparently doesn't show up with current develop. Upcoming work such as field-sensitivity causes simplification to fail, because of the type inconsistency that boolbvt::get currently might introduce.

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[kroening]

Those untyped expressions trouble me...

[tautschnig]

Those untyped expressions trouble me...

Ack. We should benchmark whether there really is much value in those clock types being as-small-as-possible. Maybe it's just fine to make them size_type() or so.

[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 32a5f76).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/103892078