PR1677: Update PaX support to detect running PaX kernel and use newer tools

2014-02-19  Andrew John Hughes  <gnu.andrew@member.fsf.org>

	PR1677: Update PaX support to detect running PaX
	kernel and use newer tools
	* NEWS: Updated.
	* acinclude.m4:
	(IT_HAS_PAX): New macro to detect whether the running
	kernel uses PaX.
	(IT_WITH_PAX): Rewritten to search for PaX tools -
	currently paxmark.sh, paxctl-ng, chpax and paxctl -
	and fail if a tool isn't found and a PaX kernel is
	being used.