Refactorings.

* tools/stage.jam
  (update-location,construct-special-target,construct-regular-target): New
  methods
  (construct): Rewrite in terms of the above methods.

Patch from Pedro Ferreira.


[SVN r21318]

tools/build

@@ -1 +1 @@
-Subproject commit 8daec2f3bcf786f0bc227121e53ebab873950635
+Subproject commit 3057d9c71839b491ba743e59a27246feca59868c