Fix re: and glob: patterns in .hgignore (reported by Brad Schick)
relglob: and relre: were already detected for a long time, so
I kept this undocumented functionality, especially as it was already
tested in test-hgignore.
% file replaced with directory
adding a
% should fail - would corrupt dirstate
abort: file named 'a' already in dirstate
% directory replaced with file
adding a/a
% should fail - would corrupt dirstate
abort: directory named 'a' already in dirstate
% directory replaced with file
adding b/c/d
% should fail - would corrupt dirstate
abort: directory named 'b' already in dirstate