* new/builtin.jam
(lib-generator): Remove.
(lib-target-class): New class. Target class is more powerfull then
generator, here.
* new/generators.jam
(construct): New argument 'return-all'.
* bew/property-set.jam
(property-set.add-raw): New method.
[SVN r18917]
are communiated via return value of 'abstract-target.generate', not as
attribute of virtual target. The advantage is that we can return usage
requirements, even if no targets were created.
Also, usage requirements is not really attribute of virtual target. If several
virtual targets are created for one main target, the previous code would set
the same usage requirements on all virtual targets.
[SVN r18689]