Update examples in the datatype chapter

[bosilca]

Problem

Example 5.11: the description is incorrect. More precisely "Each of the sends matches any of the receives." might suggest a real matching, instead of the type matching which is what the example tries to do.

Example 5.22 is unreadable. mpi-standard/642 is not at fault, the example was unreadable before, but now it just became visibly unreadable.

Proposal

Improve the readability of these 2 examples.

Changes to the Text

Impact on Implementations

None.

Impact on Users

More meaningful examples.

References and Pull Requests

[wesbland]

This wasn't read at the December 2022 meeting. The last opportunity for MPI 4.1 is to have it ready at the March 2022 meeting (and it needs to "pass" the reading).

@bosilca Are you (or is someone else) planning to push this forward or should we move it out of the plan for MPI 4.1?