* lib/pipeline.c (get_line): A short read isn't a reliable way to detect
end-of-file.  Instead, keep track of the previous buffer length returned
by get_block; if we get the same length twice in a row then that
indicates EOF.
* tests/reading_long_line.c: Rename to ...
* tests/read.c: ... this.  Update build system and test names to match.
(slow_line_helper, test_read_readline_slow): New test.