Improve the error messages produced by C-based tools in case of issues
with the command line options:
- explicitly mention to use -a/-d (and -A/-D in virt-diff)
- when extra arguments are found, mention the correct way to pass
options to certain command line switches (like --format)
- in virt-inspector, give a cleaner error message when neither -i nor
any -m is specified
In all the cases, keep the extra notice to use 'TOOL --help' to get more
help with it.
dc02e8985f