unit tests for x., i. prefixes on join by EACHI, closes #732 (#2945)
unit tests for x., i. prefixes on join by EACHI, closes #732 (#2945)


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