This resolves#1825
The basic idea is that we prefix every sequence number with its with,
separated by a dot. That way the filename length isn't increased
drastically (unlike using a fixed whidth number with 0-padding)
and the file names will be lexicographically ordered.
Remove the use of relative paths. A header at foo/bar.h could be included by
files under foo/ with "bar.h", but would be included everywhere else as
"foo/bar.h". Adjust so that every include references such a header with the
latter form.
Signed-off-by: Robert Escriva <rescriva@dropbox.com>