Do not try to drain the input pipe before closing the archive.

Do not try to drain the input pipe before closing the archive.

* src/buffer.c (close_archive): Remove call to
sys_drain_input_pipe. Pass hit_eof as the second
argument to sys_wait_for_child.
* src/common.h (sys_drain_input_pipe): Remove
(sys_wait_for_child): Declare second argument.
* src/system.c (sys_drain_input_pipe): Remove.
(sys_wait_for_child): Take two arguments. The second one helps to
decide whether to tolerate child termination on SIGPIPE.