add a few more patterns to .gitignore

Signed-off-by: Bob Copeland <copeland@lastpass.com>
add embeddable doubly-linked lists from Linux

This will provide some better primitives for manipulating the lists
while allowing accounts to be on multiple lists at the same time.

Signed-off-by: Bob Copeland <copeland@lastpass.com>
add find_matching_accounts() which returns multiple matches

This will subsequently be used to allow show.c to better handle
multiple matches.  For now, find_unique_account uses this machinery
and aborts (as before) if multiple matches are found.

Signed-off-by: Bob Copeland <copeland@lastpass.com>
show: display multiple matching entries

When an account name is listed more than once, currently lpass
will just exit with an error when searching on that name.  Instead,
list all the ids so the user can display them both.

Signed-off-by: Bob Copeland <copeland@lastpass.com>