vcd dump for Mem & ROM
Enable Mem seqRead sanity checks with --debugMem

...rather than doing so iff using C++ backend.
Remove genMuxes; generate Mux trees on the fly

This removes a lot of complexity, for backend passes in particular.
Fix FAME backend Module stack error
For Mem[Aggregate], use toBits before writing
Merge pull request #200 from ucb-bar/MemVCD

vcd dump for Mem & ROM
Allow legacy calls to toBits() (with the parens)
Vtests: change the output format of harnessMap
check snapshots before finishing the test
merge master