pacman: add --confirm option

--confirm cancels the effect of a previous --noconfirm.  This makes it
easier for scripts to default to --noconfirm but allowing users to
override it.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
pmtest: allow tests to specify binary

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
pmrule: make backup file test more robust

This prevents an exception in the event backup entries are not in the
correct format and brings the test in line with alpm's backup parsing
which splits on the last tab rather than the first.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
add pacman-db-upgrade test

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>