Fixed: forgot to export VirtualByteString and Coders in Base.
Added FloatToInt.
Added a viable implementation of BootURL.open.

This allows {New Open.file init(url:U)} to work when U is
actually a file name.
Changed the class format: contain records instead of dictionaries.

In the previous class format, a class would contain dictionaries
for things such as methods and inheritance-related information.
Because a class needs to be serialized, but a dictionary cannot,
there was a hackish thing that marked a dictionary "safe" to be
serialized.

In effect, we can consider a dictionary as safe if it won't be
changed later. But an immutable dictionary is ... a record!

So now we store records for these things in classes. The frees
us from the hackish stuff.
Use the Boot builtin module to find builtin modules.
Reviewed the way that <Base> and the boot MM are accessed.
Major simplification of BootBase.oz.
merge
Merge branch 'master' of git://github.com/mozart/mozart2-library