Fix the import handling in "complex" cases. When looking a.b.c and 'a' is a

module, we should look for 'b' *just* in the module 'a' and then continue
resolving b.c in the environment created by updating *with* a.

Still not 100% correct, but getting there.

src/Makefile

@@ -447,6 +447,7 @@ TEST_XFAILS_RUSTC := $(filter-out \
                         import3.rs \
                         import4.rs \
                         import5.rs \
+                        import6.rs \
                         item-name-overload.rs \
                         large-records.rs \
                         lazy-init.rs \