dirstate: move dropping of folded filenames into the dirstate map...
dirstate: move dropping of folded filenames into the dirstate map
When dropping files from the dirstate, the corresponding entry in the
filefoldmap is also dropped. Move this into the dirstate map object. A future
implementation of the dirstate will maintain the filefoldmap differently.
Differential Revision:
https://phab.mercurial-scm.org/D1343
