* new/builtin.jam: Made 'toolset' and 'variant'
features symmentic. Document and fix the 'variant' rule.
* new/virtual-target.jam: Refactoring attempts. Split
virtual-target into virtual-target and derived from it
file-target. Eliminate some duplication in setting target
locations.
[SVN r16437]
* new/targets.jam
(abstract-target.name): New method.
(abstract-target.project): New method.
(main-target-alternative): Simplify. Only register
main target alternative. Don't to fancy processing
of arguments.
(main-target-requirements): New rule.
(main-target-use-requirements): New rule.
(main-target-default-build): New rule.
[SVN r16249]
* new/virtual-target.jam (virtual-target): Eliminate 'subvariant'
attribute. Use properties of action to for the same
purpose.
* new/testing.jam: Induced changes.
* new/make.jam: Induced changes.
* new/generators.jam: Induced changes.
[SVN r16128]