largefiles: treat status of cache missed largefiles as "missing" correctly "hg status" may treat cache missed largefiles as "removed" incorrectly. assumptions for problem case: - there is no cache for largefile "L" - at first, update working directory to the revision in which "L" is not yet added, - then, update working directory to the revision in which "L" is already added and now, "hg status" treats "L" as "removed". current implementation does not allocate entry for cache missed largefile in ".hg/largefiles/dirstate", but files without ".hg/largefiles/dirstate" entry are treated as "removed" by largefiles extension. "hg revert" can not recover from this situation, but "rm -rf .hg/largefiles", because it causes dirstate rebuilding. this patch invokes normallookup() for cache missed largefiles to allocate entry in ".hg/largefiles/dirstate", so "hg status" can treat it as "missing" correctly.