[boost] Spirit example typo

From: Michael Walter (cm_at_[hidden])
Date: 2003-06-18 09:28:00

In http://www.boost.org/libs/spirit/doc/number_list.cpp.html,
  using namespace spirit
should read
  using namespace boost::spirit;
I think. Apologies if this is the wrong list for such an unimportant
report ;)

- Michael