tools: add configure --with-dumpdir=DIR option

The current base directory /var/xen/dump for domU dumps will be patched
to /var/lib/xen/dump by most distros to follow FHS.

This change does three things:
 - change the default from /var/xen/dump to /var/lib/xen/dump
 - provide a configure option to avoid patching the source.
 - update docs to refer to the new default location

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[ ijc -- s,/var,LOCALSTATEDIR, in help test, ran autogen.sh ]

m4/paths.m4

@@ -62,6 +62,12 @@ AC_ARG_WITH([sysconfig-leaf-dir],
 CONFIG_LEAF_DIR=$config_leaf_dir
 AC_SUBST(CONFIG_LEAF_DIR)
 
+AC_ARG_WITH([xen-dumpdir],
+    AS_HELP_STRING([--with-xen-dumpdir=DIR],
+    [Path to directory for domU crash dumps. [LOCALSTATEDIR/lib/xen/dump]]),
+    [xen_dumpdir_path=$withval],
+    [xen_dumpdir_path=$localstatedir/lib/xen/dump])
+
 if test "$libexecdir" = '${exec_prefix}/libexec' ; then
     case "$host_os" in
          *netbsd*) ;;
@@ -113,4 +119,7 @@ AC_SUBST(XEN_LOCK_DIR)
 
 XEN_PAGING_DIR=$localstatedir/lib/xen/xenpaging
 AC_SUBST(XEN_PAGING_DIR)
+
+XEN_DUMP_DIR=$xen_dumpdir_path
+AC_SUBST(XEN_DUMP_DIR)
 ])