Merge cmucl simple-streams

Merge cmucl simple-streams

... major code shifting: simple-streams.lisp is no more; its contents
    have moved into several  files, each for a specific kind of stream
... file layout is now the same as cmucl pcl/simple-streams directory
    for easier trading of fixes / functionality
... new functionality: external formats (need some work still, but
    infractructure is there), string-streams
... Some functionality still missing (see TODO file)