patmos: minor extension of graph traits

* pass the graph itself to the isNodeHidden callback
* subgraphs for machine-level call graphs
* update the users of isNodeHidden
patmos: extend stack cache analysis

* compute max stack occupancy for SCCs in the call graph (recursion)
* construct and solve ILPs to do that
* simple interface to supply LP user annotations to limit recursion depth
* simple data-flow analysis to find functions with at least one call-free path