The .tag member was used for "debugging", but it was actually always set to NULL and never ever read, so this commit just removes it and remove isc_mem_gettag() and modifies isc_mem_setname().
The .tag member was used for "debugging", but it was actually always set to NULL and never ever read, so this commit just removes it and remove isc_mem_gettag() and modifies isc_mem_setname().