Unify diff_opts and make it clear it is global
Add -v (verbose) and make default output smaller/cleaner (unless -v is given)
Remove a few empty ref/*.stdout - not needed anymore.
remove empty ref/*.stdout reference files
more accurate result to avoid "precision differences ignored"
Add verbosity level, switch system->mysystem
Fix uninitialized value $opt_v when -v is not in effect
Clean up Windows cases a bit (better prints, and consistent indents)
Recreate all "minor differences ignored" references to be 100% accurate now that Vaclav figured out the diff -W ... bug
Remove more empty *.stdout file references which are no longer needed.