Un-xfail test that works. Closes #2883

Author: catamorphism

src/test/run-pass/class-separate-impl.rs

@@ -1,6 +1,4 @@
-// xfail-test
 // xfail-fast
-// (Not sure why, though -- FIXME #2883)
 import to_str::*;
 import to_str::to_str;