check multiple parser methods are not defined in a parser

This fixes a bug introduced in be4a2117494ce73750cec3fd3c7cb4a60e722bcf.

The old commit(be4a21) checked only the case that allparser, parser2 and parser_with_gc
were not set but didn't check more than one were set. This patch checks this case, too.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
refactor: rename TrashBoxDestroy to TrashBoxDelete

made the name align to convention used in other APIs.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
add trashBoxFree

trashBoxFree does trashBoxTakeBack for an item given
as an argument and free the item with its destrctor
specified when doing trashPut the item.

This API is suggested by @b4n in #90.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>