This commit introduces a change in AdvancedValueInfoMFI which forces to
consider constraints valid on 32-bit values to be valid on their
untruncated 64-bit counterparts.
While being unsound, this is important to easily devirtualize indirect
branches on 64-bit architectures where often constraints are expressed
on 32-bit switch values.
`ValueMaterializer` is a rewrite of what was called `AdvancedValueInfo`
which follows the same principles.
The main benefits over the old version is:
* We materialize the data-flow graph and the CFG of the relevant part of
root. This makes debugging significantly easier.
* We drop the old MonotoneFramework infrastructure in favor of
getMaximalFixedPoint.
* We significantly reduce the amount of queries we make to
AdvancedValueInfo.
Alessandro Di Federico