Fixed buggy jamfile.

When building from top-level boost-book build, incorrect path to
header files was corrupting the whole build.


[SVN r23566]

libs/logic

@@ -1 +1 @@
-Subproject commit cf7fe4cb56104b099bb036aaa62b5e9c8480c0a7
+Subproject commit cdb51dda6ef6d7a1bd02acca00daace788019abe