Issue warning messages for missing parameterized modules and attempts to set initial values.
Replace simple "if (cell-type)" with "else if" chain.
Fix FIRRTL shift handling.
Add support for parameterized modules, $shift, $shiftx.
Handle default output file.
Deal with no top module.
Automatically run pmuxtree pass.
Allow EXTRA_FLAGS and SEED parameters to be set in the environment for tests/tools/autotest.mk.
Support FIRRTL regression testing in tests/tools/autotest.sh
Add xfirrtl files to test directories to exclude files from FIRRTL regression tests that are known to fail.