* New feature <relevant> which is automatically deduced in most cases.
* Features which are not relevant do not affect target paths and
do not prevent merging of virtual targets.
* generators.jam: generator.run always returns usage-requirements
to allow usage-requirements in non-top-level generators. This
is necessary because we're using usage-requirements to track
relevance from flags.
* New rule toolset.uses-features to specify features that the rule
checks manually, instead of using toolset.flags. In the future,
we should consider restricting the properties actually passed,
to detect errors.
* Adjust tests to handle the new paths (verified by inspection).
* Add temporary option --ignore-relevance to consider all features relevant
to aid migration.
* New rule property.evaluate-conditional-relevance which helps tracking
relevance in <conditional>.
* Widely scattered changes to use the new interfaces.
* Fix problems in x-product that could make it return extra property-sets
in complex cases. Also clarify exactly what it is supposed to do.
* free_features_request.py: This is subsumed by the new test.
* direct_request_test.py: This is mostly subsumed by the new test
except for the last test for chained build-projects, which doesn't
make much sense in the current code base as build-project is implemented
very differently.
* Document using / to separate properties.
This uses quickbook to add an appendix of examples directly from the
source tree. The inclusion of the examples is done with glob so that we
can just add examples by having a "readme.qbk" in the example we want to
document.
This makes the content appear in the top 'index.html' element,
and disappear form TOC. I could not find another way - disabling
chunking for the first section would almost work, but would retain
it in TOC.
