Run cascade delete only for source's range is same as index's domain

Cascade delete feature is introduced to avoid dangling references. If
source's range is different with index's domain, the case doesn't
cause dangling references. So we don't run cascade delete for the case.

Not referenced case (This case's behavior is changed. Cascade delete
isn't ran.):

    table_create Users TABLE_HASH_KEY ShortText
    table_create URLs TABLE_HASH_KEY ShortText

    column_create Users bookmarks COLUMN_VECTOR ShortText # <- Not URLs type!

    column_create URLs bookmarks_index COLUMN_INDEX Users bookmarks

Referenced case (This case's behavior isn't changed. Cascade delete is
ran.):

    table_create Users TABLE_HASH_KEY ShortText
    table_create URLs TABLE_HASH_KEY ShortText

    column_create Users bookmarks COLUMN_VECTOR URLs # <- URLs type!

    column_create URLs bookmarks_index COLUMN_INDEX Users bookmarks

[groonga-dev,02073]

Reported by yoku. Thanks!!!