Rework \@advisor to use scratch \count@ instead of advisor@loop.

Rework \@advisor to use scratch \count@ instead of advisor@loop.

I thought the end of the group would deallocating my advisor@loop
counter.  I was wrong :p.  Turns out deallocating counters in (La)TeX
is hard (see the localloc package for details).  The easier solution
is to use scratch counters, which led to a few of LaTeX -> TeX
adjustments.  Anyhow, now I don't waste a counter running \@advisor.

Also corrected a typo in the documentation: \@advisor is used by the
abstract environment, not \maketitle.