[PATCH 00/17] Standardize c/r error reporting

[serue at us.ibm.com]

From: Serge E. Hallyn <serue at us.ibm.com>

This patchset
	1. defines ckpt_error() 
	2. allows users to pass a logfd into sys_checkpoint and
	   sys_restart
	3. Switches ckpt_write_err() to accepting a single enhanced
	   format string, instead of two separate formats.
	4. Has ckpt_write_err() call ckpt_error() to also log the
	   error in the user-provided logfile and syslog.

Every ckpt_error() message is prefixed by current's global pid,
current's virtual pid, number of bytes read/written, and the
ctx->errno.

I'm sure we'll want another round if only to alter the format,
but I'm finding it very useful as is.

(As more callers are added I expect we'll want to add %(A) to
the format to indicate active_pid should be printed).

-serge