Make some refactoring.

* 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]

tools/build

@@ -1 +1 @@
-Subproject commit d1076d3c1a6f31c6db45b3e5ac3fefc98ff68dfe
+Subproject commit e147aa0b32c16d5eceb797c50237674b54e5a9ee