Make lazyindex load slightly faster

Simplify checkout slightly, replace checkdir with os.makedirs

Sort files on check-in for good I/O patterns

Make compression more intelligent: - we don't attempt to compress things under 44 bytes (empirical) - we check whether larger objects actually compress - we tag objects to indicate their compression NUL means uncompressed and starts with NUL x means gzipped and starts with x (handy) u means uncompressed, drop the u

Add script for doing conversion of repo from oldstyle to newstyle

Move hg from storing files in data with base64 encoding to full pathnames with .i and .d extensions. This means we naturally get good FS layout, and cp and tar fix things up nicely rather than pessimizing layout.

Annotate was being too clever trying to work in place, and triggering its assert. Simplify it, fix it, and speed it up a tiny bit.

Warn if we fail to truncate something