Added new tests related to Boost Build's default toolset handling. They test that the correct default toolset gets use and that when it gets used that has no different status than any other explicitly specified toolset.

[SVN r42549]

tools/build

@@ -1 +1 @@
-Subproject commit 35d1831f4f6da151226e6c168175fffe2dc6d3dd
+Subproject commit 475813d4ba7c34ec38680c261f6edf4b05769e8e