Spaces now only ignored around items in the argument of function/macro

Previously, the argument of \begin{macro} or \begin{function} was read with
a particular set of catcodes.  With recent changes came the use of \clist_map
which does space stripping to go through the list of macros.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5319 de43f980-851b-0410-b2f7-c40aca1f87e0