If the c_overviewer module is present but will not import, provide a
different error than if the modules doesn't exist at all.
Also, added a new mechanism to force users to re-build their extension
if needed (see the top of overviewer.h)
Specifying listify on an option will cause it to be parsed as a list.
Use listdelim to specify the delimiter (defaults to ',')
Examples, assuming you had the following option:
add_option("--test","test", type="int", listify=True)
Command line:
--test 1 results in [1]
--test 1,2,3 results in [1,2,3]
Config file:
test=1 results in [1]
test="1,2,3" results in [1,2,3]
test=[1,4,9] results in [1,4,9]
