Added basic tests of unique and duplicated for integer64 columns
Added basic tests of unique and duplicated for integer64 columns

vlulla/data.table,jangorecki/data.table,Rdatatable/data.table,jangorecki/data.table,Rdatatable/data.table,jangorecki/data.table,vlulla/data.table,vlulla/data.table,vlulla/data.table,jangorecki/data.table,Rdatatable/data.table,Rdatatable/data.table