Mimimal support for the 'flags' rule.

* new/toolset.jam: New file.

* new/virtual-target.jam (action.actualize):
    Call 'toolset.set-target-variables'.

* new/gcc.jam: Use flags for compiling.


[SVN r16189]

tools/build

@@ -1 +1 @@
-Subproject commit 279c8ef3f8725e2f4727f48af7353433a15c68a1
+Subproject commit 7272ef9f42abd7f3a965107e511fa24f670ee83c