MPI_Start text should reflect rules for partitioned P2P communication matching

[cniethammer]

Problem

The Point to Point chapter sates in MPI 4.0 section 3.9

A send operation started with MPI_START can be matched with any receive operation
and, likewise, a receive operation started with MPI_START can receive messages generated
by any send operation.

This seems to have been overlooked with the introduction of partitioned P2P communication in MPI 4.0 section 4.2.1- which uses MPI_Start, too, and comes with the following, contradicting matching rule:

... This operation (partitioned communication from MPI_Psend_init) can only
match with partitioned communication initialization operations, therefore it is required to
be matched with a corresponding MPI_PRECV_INIT call.

Proposal

Take care of the matching rules for partitioned communication in this part of the P2P text

Impact on Implementations

Clarification of the text.

Impact on Users

Clarification of the text.

References and Pull Requests