[RFC] Header reorganization finish up

[David Ayers]

Hello,

It's finally in.  Yet there remain a few issues.

- UnixFileHandle.[hm] and WindowsFileHandle.h seem very obsolete and are 
not being build.  I haven't reinserted these headers yet.  Please either 
remove the corresponding *.m file and check with configure.ac whether 
the comment still applies, or ask me to put the headers back (public or 
private).

- I had to split the -gui documentation into two projects similar to 
base.  They are not integerated well and still require some cleanup.

- I didn't move all private headers to the source directories.  I'll 
explain why tommorrow.  (Need sleep!)

Otherwise I'd like to thank you all for helping me make this happen!

Cheers,
David