find: Support --print0

It would be nice if command-specific options were supported. The first
difficulty is that which command is being called is not known until after
getopt; but that could be worked around by finding the first non-dashed
parameter. Storing the settings without putting them in the annex monad is
the next difficulty; it could perhaps be handled by making the seek stage
pass applicable settings into the start stage (and from there on to perform
as needed). But that still leaves a problem, what data type to use to
represent the options between getopt and seek?

Annex.hs

@@ -60,6 +60,7 @@ data AnnexState = AnnexState
 	, force :: Bool
 	, fast :: Bool
 	, auto :: Bool
+	, print0 :: Bool
 	, branchstate :: BranchState
 	, catfilehandle :: Maybe CatFileHandle
 	, forcebackend :: Maybe String
@@ -82,6 +83,7 @@ newState gitrepo = AnnexState
 	, force = False
 	, fast = False
 	, auto = False
+	, print0 = False
 	, branchstate = startBranchState
 	, catfilehandle = Nothing
 	, forcebackend = Nothing