buf: stream: switch approach for unget_char.

We switch to the method used in string streams for
ungetting characters, whereby we UTF-8 encode the pushed
back character and push back the subsequent bytes,
thereby unifying character and byte pushback.

* buf.c (struct buf_strm): Remove member unget_c.
(buf_strm_mark): Remove reference to unget_c.
(strm_get_char): Remove code for obtaining previously
pushed back character from s->unget_c stack.
(buf_strm_unget_char): Rewrite using the approach
of using utf8_encode to write the multi-byte representation
of the character into utf8_tiny_buf, and then
pushing back the bytes.
(make_buf_stream): Don't initialize removed unget_c.

* tests/018/streams.tl: New tests.

0 files changed, 0 insertions, 0 deletions