Providing vc-dir-state from vc-fossil.el

Since then I did a bunch of modifications.  What I didn't like at all was the total hack that needs-merge and needs-patch turned out to be.   After posting a stupid question on fossil-users, I realized what I really wanted was to know if the file would update if the fossil update command was invoked.  So I changed vc-fossil-state to use update.   Also added a vc-fossil-dir-state to make the VC under dired go a lot faster.

Found out last night that the vc-*-dir-state is called for every directory in the tree and is expected to return the status for only the files in that dir, not for the subdirs.

So I changed the update command to add these flags.

• -n | --nochange : do not change any files, but go through the motions.
• --local                : do not autosync even if autosync is on in the settings
• -v                       : verbose, print messages even for UNCHANGED and EDITED
• --file name       : only print status for file name.  If name is a directory, print status for files in that directory, but not for subdirectories.

Now C-x v d on the fossil tree takes a few seconds.   There's more speedup that can be done in update.c to filter out the subset earlier in the function if the --file flag is specified.