parallel_mode.xml: Documented the new choices, factoring out common tags.

2008-05-16  Johannes Singler  <singler@ira.uka.de>

         * doc/xml/manual/parallel_mode.xml:
         Documented the new choices, factoring out common tags.
         * include/parallel/multiway_merge.h:
         Place comparison functor at the end, to comply with
         established convention.
         (parallel_multiway_merge) Pass number of threads explicitly.
         Introduce new compile-time variants, make exact splitting the
         default.
         * include/parallel/tags.h:
         Extend exact_tag, introduce sampling_tag.
         * include/parallel/merge.h:
         (parallel_merge_advance) Adapt to changed interface.
         * include/parallel/multiway_mergesort.h: Likewise.

From-SVN: r135411