Snapshot of SVN 4742

The major change in this snapshot is allowing expl3 to be loaded
using formats other than LaTeX2e:

  \input expl3-generic %

This allows the 'programming' layer to be used in a
format-neutral way.

Minor changes to the bundle include:

 - Further improvements to native driver code
 - Improve handling of class options by l3keys2e
 - Fix nesting of \keys_set_known:nnN
 - Various documentation tweaks and typo fixes

There is also one removal from l3experimental: l3dt/xmetadata is
dropped as while some of the ideas are useful, the existing
implementation is too slow to be useful.

Please allow a couple of days for this to propagate around the CTAN
Joseph Wright