Log Message:
tex-elsarticle{,-doc}: update to 3.1

In this version 3.1 we have slightly modified the \tnotemark defnition
to fix a "missing number" LaTeX error on the first LaTeX run (before
the labels are written to the aux file). elsarticle.dtx is modified for
this.  Earlier, this was a problem with editors that break compilations
on LaTeX errors (such as LyX).