Initialise 'padding'

I don't like random data appearing in output. Even if it's redundant.
Specify which exceptions can be handled in a 'try...except...' statement.
Options for packing source code set from CMake...

...this probably breaks the Makefile.
Merge remote branch 'origin/master' into mbda
Merge remote-tracking branch 'mbda/mbda' into mbda
Fixed GIT_DIR variable and a Python exception.
Fixed pack.py to work with python 2.4 to 3.x