* tests/init.cfg (skip_test_): Remove function.
Use skip_ in place of skip_test_ everywhere else.
* cfg.mk (sc_prohibit_skip_): Remove rule.
* tests/**: Use skip_, not skip_test_, everywhere.
* src/split.c (main): Exit with a diagnostic if --filter
is specified along with a specific chunk number.
* test/split/filter: Ensure this combination fails.
* src/split.c (bytes_split): Stop reading when we
can no longer write to a child process.
(lines_rr): Likewise.
(lines_bytes_split): No change is made here since
input is bounded by the original file size.
* test/split/filter: Add test cases.
src/split.c (main): Don't unblock SIGPIPE before cleanup,
as then any pending signals will be sent and cause
the main split process to exit with a non zero status (141).
* test/split/filter: Add a test for this case.
skip_test_ emits its diagnostic both to FD 9 (tty), and to
FD 2 (usually the log file), whereas init.sh's skip_ emits
only to FD 9. Without that, the log is slightly less useful.
* tests/cp/fiemap-2: Use skip_test_, not skip_.
* tests/cp/fiemap-perf: Likewise.
* tests/du/bigtime: Likewise.
* tests/du/files0-from-dir: Likewise.
* tests/du/move-dir-while-traversing: Likewise.
* tests/init.sh: Likewise.
* tests/misc/sort-stale-thread-mem: Likewise.
* tests/misc/stat-nanoseconds: Likewise.
* tests/mv/i-3: Likewise.
* tests/mv/sticky-to-xpart: Likewise.
* tests/split/filter: Likewise.
Prompted by a report from Pádraig Brady.
