Fix file-changed-to-dir and dir-to-file commits (issue660).
Allow adding to dirstate files that clash with previously existing
but marked for removal. Protect from reintroducing clashes by revert.
This change doesn't address related issues with update. Current
workaround is to do "clean" update by manually removing conflicting
files/dirs from working directory.
adding da/foo
adding foo
% manifest
200 Script output follows
drwxr-xr-x da
-rw-r--r-- 4 foo
200 Script output follows
-rw-r--r-- 4 foo