multipath-tools: check header file instead of intalled lib

multipath-tools: check header file instead of intalled lib

Hi,
attached patch checks the header file instead of an installed lib for
dm_task_struct. Since distros have this lib add different patchs the
check should be more reliable.
Cheers,
 -- Guido

From: =?UTF-8?q?Guido=20G=C3=BCnther?= <agx@sigxcpu.org>
Date: Sun, 30 Aug 2009 13:38:55 +0200
Subject: [PATCH] check header file for defintion of dm_task_no_flush

instead of checking the so for the symbol (which seems to be hard to
find).