Add MultDepth Analysis

[pjattke]

In v1.0, we had a MultDepthVisitor that determined the multiplicative depth of variables, which might be handy to port over.

Note that the visitor in v1.0 does not work properly if an If-statement that contains an Else-branch is involved.

The statement following an If-statement, i.e., the statement after the Else-branch's closing bracket if (...) { ...} else { ... } must take the "highest depth" of a variable by comparing the calculated depth of both branches.