Allow for e.g. mylatexformat when expl3 is loaded with LuaTeX

As suggested by HO, this ensures that the equivalent of \pdfstrcmp is
available even if the package code is built into a format.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4766 de43f980-851b-0410-b2f7-c40aca1f87e0
Lua scripts: only hide 'check' output but not 'checklvt'


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4767 de43f980-851b-0410-b2f7-c40aca1f87e0