Change default-build handling.

* new/targets.jam
     (main-target.apply-default-build): Combine build request with
     default build.

* new/default_biuld.py: More tests.


[SVN r17756]

tools/build

@@ -1 +1 @@
-Subproject commit 182a36e139c8aa2e2f0c7eec43fb2b81355ce09a
+Subproject commit e922b1c0cfd242cd7ceb5617b45b86c68374f6dd