Updated tex/latex

  * misc/pmom.sty: new package, code to put a mark on margin, code
    borrowed from 'olympiad.dcf' with small improvements;
  * isuth-modules/olympiad.dcf: commented 'swap-greeks' package and put
    'mathug2', this change is NOT TESTED!

Signed-off-by: Vladimir Lomov <lomov.vl@gmail.com>