Clean up Separation of items in Deprecated, Deleted and Backwards compatibility chapters

[schulzm]

Problem

The three chapters deprecated, deleted and backward incompatible contain several unrelated topics. During the review for MPI 4.0 we detected that this led to having no space between, which makes the chapters hard to read. For MPI 4.0 we added a quick hack to add seperators, but this is not the ideal solution

Proposal

Add special latex environments with headings (tbd. whether they should be in the TOC or nor) that adds separate headings for each item

Changes to the Text

Add headers between items in chapters 16-18

Impact on Implementations

None

Impact on Users

Standard more readible

References

PR 745

[RolfRabenseifner]

In MPI-4.0, Section 16.3 Deprecated since MPI-4.0, I would add the following subsubsections:

• 16.3.1 Formerly in Section~\ref{sec:cancel} % 3.8.4: Cancel of send requests
• 16.3.2 Formerly in Section~\ref{subsec:info} % 10: MPI_INFO_GET and MPI_INFO_GET_VALUELEN
• 16.3.3 Formerly in Section~\ref{sec:mpit:retcodes} % 15.3.10: MPI_T_ERR_INVALID_ITEM
• 16.3.4 Formerly in Section~\ref{f90:types} % 19.1.9: MPI_SIZEOF

In addition, in the change-log, B.1.2 Changes in MPI-4.0, Item 33

Section 16.3 on page 786.
MPI_SIZEOF was deprecated.

the references should be

Sections 16.3 and 19.1.9 on page 786 and 809.

That's all what I would add/change in this issue.

[wgropp]

I would not add subsections. This is really an example of something where an unnumbered list (itemize environment) is probably most appropriate.