Check for libdevmapper header

configure.ac

@@ -863,6 +863,12 @@ if test x"$enable_device_mapper" = xno ; then
   device_mapper_excuse="explicitly disabled"
 fi
 
+if test x"$device_mapper_excuse" = x ; then
+  # Check for device-mapper header.
+  AC_CHECK_HEADER([libdevmapper.h], [],
+               [device_mapper_excuse="need libdevmapper header"])
+fi
+
 if test x"$device_mapper_excuse" = x ; then
   # Check for device-mapper library.
   AC_CHECK_LIB([devmapper], [dm_task_create], [],