devtools: give some hints for ABI errors

devtools: give some hints for ABI errors

abidiff can provide some more information about the ABI difference it
detected.
In all cases, a discussion on the mailing must happen but we can give
some hints to know if this is a problem with the script calling abidiff,
a potential ABI breakage or an unambiguous ABI breakage.

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Ray Kinsella <mdr@ashroe.eu>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Aaron Conole <aconole@redhat.com>