Load Heiko's pdftexcmds in l3trial/l3benchmark.dtx

The package uses \pdf@elapsedtime and \pdf@resettimer from the
package pdftexcmds when using LuaTeX, but I forgot to load it.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5025 de43f980-851b-0410-b2f7-c40aca1f87e0
Step copyright year in l3benchmark.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@5026 de43f980-851b-0410-b2f7-c40aca1f87e0