Test for poor main's per-source requirements.

    * new/builtin.jam: Make 'obj' main type.
    * new/generators-test/*: Try compiling the same CPP file with
        different defines and linking in the same exe.


[SVN r15649]

tools/build

@@ -1 +1 @@
-Subproject commit 9ad477276cf292bbd0ec1ad24d9557a2e4b8ae61
+Subproject commit 4af9e4371fd11097e576766c407b9eb257442307