Fix revlog-ng interaction with old-http. revlog.py wasn't trying to detect the version of a revlog file that doesn't exist on the filesystem (as is the case with old-http). Additionally, there was an off-by-one error in httprangereader.read (ranges in HTTP Range headers are inclusive), making it get more data than what was asked for. This made a struct.unpack complain that "unpack str size does not match format". Finally, with the two fixes above, test-static-http fails, since BaseHTTPServer doesn't understand ranges and returns too much data. Work around that by reading only the specified amount.

pulling from ../a
searching for changes
abort: repository is unrelated
pulling from ../a
searching for changes
warning: repository is unrelated
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
(run 'hg heads' to see heads, 'hg merge' to merge)
changeset:   1:bdcee5d51fa6
tag:         tip
user:        a
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     a

changeset:   0:f155ba1aa5ba
user:        b
date:        Mon Jan 12 13:46:40 1970 +0000
summary:     b