Extend Load.java to allow loading FASLs from arbitrary streams

[ehuelsmann]

Currently, Load.java inspects a file to find whether or not this file is a ZIP file. From there, it decides on a strategy to continue loading the file.

However, in many circumstances in Java one has a stream of unknown origin. It's a requirement for good Java integration to be able to load FASLs off arbitrary streams (resource streams, e.g.).

[ehuelsmann]

There's more to this than meets the eye: we currently depend on random access to the streams of FASLs to load the .cls files in the order specified by the textual loader file (._ file).

In addition, we depend on opening the same ZIP file twice because we load the '._' file at the same time as the .cls files. This is also not possible when loading off a stream.

The current preloading API should help resolve this issue.

[ehuelsmann]

Duh. It's not addressed.

[Mark Evenson]

Again this should be fairly easy, but we'll bump it to the next release.

[ehuelsmann]

Note this change is *not* related to #24 and #29, which are about loading from JARs. This ticket is about loading from streams. Quite possibly, the other two can be routed through the result of this one, once it becomes available.