Bug in vtlib Module_Basic->initTables()
When you call this function to create a new module, it is still creating the $basetable_user_field
table which was the 7.0.0 format where there was a seperate user_field table for every entity module. In version 7.1 this was changed to a common table: vtiger_crmentity_user_field
http://code.vtiger.com/vtiger/vtigercrm/blob/master/vtlib/Vtiger/ModuleBasic.php#L298
There is no need for this at all any more. Lines 298 and 302 should be removed.