grn_obj_cast: add support for casting from [RECORD] to [RECORD]
grn_obj_cast: add support for casting from [RECORD] to [RECORD]

groonga/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,komainu8/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,komainu8/groonga,groonga/groonga,komainu8/groonga,kenhys/groonga,kenhys/groonga,komainu8/groonga,komainu8/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,kenhys/groonga,komainu8/groonga,groonga/groonga