Initial patch courtesy of Ariel Badichi.

- Rename RUN-TESTS to RUN and export it from BABEL-TESTS.
- New test CODE-CHAR-NILNESS checks whether we can encode all
  code points below BABEL:UNICODE-CHAR-CODE-LIMIT.
- TEST-UNICODE-ROUNDTRIP: don't try to encode non-characters.
- UTF8-ILLEGAL-CODE-POSITIONS: new test adapted from MGK's UTF8
  test suite.
- Disable a few tests for CCL: UTF-8B.* and CODE-CHAR-NILNESS.

- Add regression test: SHARP-BACKSLASH.3.

- added regression test.

- Uses DEFSTEST a lot. Should probably get rid of that.

in-memory bivalent vector-buffered streams with file-position and with-output-to-sequence (hope)fully works.

- Was calling a nonexistent function.
- Added a note about endianness to its unit test.

- Add regression tests.

- Added tests adapted from SBCL's tests/octets.pure.lisp
  (which discovered all of those UTF-8 bugs)
- Added tests against flexi-streams' ISO-8859-* tables.

- Added new tests, some of which fail.

- Added regression test: STRING-TO-OCTETS.1

- SHARP-BACKSLASH was calling UNREAD-CHAR after PEEK-CHAR and CLHS says
  the consequences of doing that are undefined.
- Added two new tests SHARP-BACKSLASH.1 and SHARP-BACKSLASH.2.

- Added regression test as well.

- Disabled for OpenMCL whose #\ already works as expected.
- Updated tests.

- Split accessors into getters and setters.  The setf expanders
  didn't work on several Lisps.
- Rewrite the UTF-8 octet counter to make CLISP happy.
- Fix coding-error :buffer initarg.
- Fix missing ONCE-ONLY macro in strings.lisp.
- Fix tests for Lispworks which doesn't understand #\uXXXX.

Supported encodings: EBCDIC-US, ASCII, ISO-8859-1, UTF-8, UTF-16 and UTF-32.