This PR handles:

- Process -> MPI process

- root process/process root/etc... -> the root / the root is clearly defined in the chapter introduction

- data type -> datatype

- using \mpiarg{} and \mpicode{} when appropriate

- and multiple small corrections that are identified by ticked boxes and the comment gathering other handled suggestions which had no box to tick in https://github.com/mpi-forum/mpi-issues/issues/341

Note that I sorted all suggestions in this issue in four separate comments:

- suggestions handled in this PR https://github.com/mpi-forum/mpi-standard/pull/806

- suggestions that were already handled in other PRs and are corrected in the current mpi-4.x branch

- suggestions that are not relevant, or that will be isolated in their own private issue

- suggestions that are not handled yet and still need to be dealt with. If the current PR passes the reading, I will create a new issue with only the remaining suggestions. I updated all pages and lines references in the suggestions. In my comment, pages and lines now refer to the official MPI-4.0 standard (much more easy to find the issue).

Best regards,

Julien J.