Apply feature defaults when building.

    * new/build-request.jam (expand-with-defaults): New rule
    * new/build-system.jam, new/targets.jam: Use 'expand-with-defaults' instead
        of 'expand'.
    * new/builtin.jam: Define new feature 'threading'.
    * test/project_test3.py: Test that feature defaults are applied.


[SVN r14307]

tools/build

@@ -1 +1 @@
-Subproject commit 3989a698e033d2f66855ce8a7de87f1b3e5211b2
+Subproject commit 0bfc1049ee5d0cc31ce622bb52a1236da0f2e9d6