Avoid using xxiobuf_read to skip with pipes.

When manually skipping bytes while parsing a pipe we use iobuf_read directly
instead of xxiobuf_read to avoid a slight performance overhead.
Fixes a bug with very large dates.

When a displayed date for a file was very large the sar command caused a
segmentation fault. The program didn't take care of the localtime
function giving an EOVERFLOW error hence returning a NULL pointer. This
patch adds a function to parse very large dates with such overflow
error.
Fix with buffered IO.

When using an archive with some large file a buf was caused in the
buffered IO.