* new/targets.jam
(main-target.select-alternative): Rewrite.
(main-target.generate-really): Issue error in all cases where best
alternative could not be found.
(basic-target.match): Renamed from 'match-rank' and changed.
* boost_build_v2.html: Document new algorithm.
* test/alternatives.py: More tests.
[SVN r20331]
Vladimir Prus