Mainly editorial tidying


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5013 de43f980-851b-0410-b2f7-c40aca1f87e0
Add a build wrapper for l3build itself

A few issues to address here, some of which are in l3build.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5014 de43f980-851b-0410-b2f7-c40aca1f87e0