Bug 1080 - Fix TestByteBufferInputStream: Handle OutOfMemoryError cause in IOException (Add note to FLUSH_NONE); Reduce test load / duration.
Bug 1080 - Add write support for memory mapped big file I/O via specialized OutputStream impl.

Added MappedByteBufferOutputStream as a child instance of MappedByteBufferInputStream,
since the latter already manages the file's mapped buffer slices.

Current design is:
  - MappedByteBufferInputStream (parent)
    - MappedByteBufferOutputStream

this is due to InputStream and OutputStream not being interfaces,
but most functionality is provided in one class.

We could redesign both as follows:
  - MappedByteBufferIOStream (parent)
    - MappedByteBufferInputStream
    - MappedByteBufferOutputStream

This might visualize things better .. dunno whether its worth the
extra redirection.

+++

MappedByteBufferInputStream:
  - Adding [file] resize support via custom FileResizeOp
  - All construction happens via ctors
  - Handle refCount, incr. by ctor and getOutputStream(..), decr by close
  - Check whether stream is closed already -> IOException
  - Simplify / Reuse code

MappedByteBufferOutputStream:
  - Adding simple write operations