All `proc_*` passes now use the same module and process for loops, using `design->all_selected_modules()` and `mod->selected_processes()` respectively.
This simplifies the code, and makes the couple `proc_*` passes that were ignoring boxed modules stop doing that (which seems to have been erroneous rather than intentional).
If width of a case expression was large, explicit patterns could cause
the existing logic to take an extremely long time, or exhaust the
maximum size of the underlying set. For cases where all of the patterns
are fully defined and there are no constants in the case expression,
this change uses a simple set to track which patterns have been seen.
o Not all derived methods were marked 'override', but it is a great
feature of C++11 that we should make use of.
o While at it: touched header files got a -*- c++ -*- for emacs to
provide support for that language.
o use YS_OVERRIDE for all override keywords (though we should probably
use the plain keyword going forward now that C++11 is established)
