Add safeties to global options variable

This is necessary if importing idifference.py as a module.

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>

Conflicts:
	python/idifference.py

(This comes from a commit in a long-ago forked development branch.  To
resolve the conflict, I had to trim away some changes to the output
report.)
Add extra, granular counters on disk state changes

(Commit time adjusted for the last commit on this subject from the
forked development branch.)

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>
Correct variable reference

This correction (from a forked development branch) resolves another
issue with calling idifference as a module: the infile variable is not
in scope if idifference is not the main module.

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>

Conflicts:
	python/idifference.py
dfxml_tool: test ../src for a quicker test
Start testing differential DFXML summary script
Merge branch 'master' into read_old_fileobjects
Import and adapt a little more of idifference