[mpiwg-tools] Problem of MPI_T_PVAR_GET_INDEX

I noticed there is a proposal to query cvar/pvar/category index by their name. The one for pvar is questionable: MPI_T_PVAR_GET_INDEX(name, pvar_index) Since the Standard reads (p577) * Advice to implementors.* Groups of variables that belong closely together, but have different classes, can have the same name. This choice is useful, e.g., to refer to multiple variables that describe a single resource (like the level, the total size, as well as high and low watermarks). (End of advice to implementors.) It implies pvar names are not unique among pvar classes. So we need to require unique pvar names, or add a pvar class argument to MPI_T_PVAR_GET_INDEX. --Junchao Zhang