Support for (FLEXI-STREAMS-like) :external-format

[ehuelsmann]

Currently the code in open.lisp ignores the external format specifier. Next to that, FileStream?.java is based off RandomAccessFile?, which doesn't allow specification of input/output formats.

Streams.java, the base stream for all streams hard-codes ISO-8859-1 as its encoding.

To support :EXTERNAL-FORMAT everywhere, we need to base our streams off InputStreamReader/OutputStreamWriter? interfaces, which allow specification of the source/target character set.

[ehuelsmann]

Beware that - when implementing this using streams in Java - it's hard to implement the file-position SETTING form of FILE-POSITION.

It looks like there's a way out though: FileInputStream? seems to return a Channel which implements SeekableByteChannel?, which in turn implements 'public int position()' and 'public void position(int newPosition)'

[Mark Evenson]

For #13 I looked at FileStream?.java . If the _setFilePosition is required even for
character streams, I think there is no easy and safe way to implement multiple
encoding handling.
But since abcl can read from network connections, on which you can't do random access,
I believe there is a way to keep the seeking requirement out of the way of
character (non-binary) streams.

-- Hideo at Yokohama via armedbear-j-devel

[ehuelsmann]

Implemented and merged to the trunk. Released in the 0.12 release.