This commit adds caching for mutual reachability among children of a
node, in SimplifyInstanceAtOffset0.
This makes the DLAStep 10% to 50% faster on real-world benchmarks we
have measured, such as `updatedb.plocate` and `df` for Ubuntu 22.04
x86_64.
Change company name to "rev.ng Labs Srl" in all license headers
to reflect changed company name and legal status
Add missing license headers to files that didn't have one
This step removes redundant instance-at-offset-0, collapsing the child
into the parent, whenever this operation does not induce instance-loops
on the graph.
This is intended to reduce the number of shallow wrapper structs and
unions.
Alessandro Di Federico