Prepare for future LLVM upgrades by setting the stack argument alignment via getByValTypeAlignment (commit r198287).
Improvements for function splitting heuristics

* Added option -mpatmos-preferred-scc-size to allow larger regions for SCCs without calls
* Always add post-dominators to subfunctions, if possible
Fix regions starting with a SCC, do not allow jump table entries in such SCCs and ensure correct order of header