Add build system

Add autoconf style build infrastructure to the ZFS tree.  This
includes autogen.sh, configure.ac, m4 macros, some scripts/*,
and makefiles for all the core ZFS components.

config/kernel-get-disk-ro.m4

@@ -0,0 +1,18 @@
+dnl #
+dnl # 2.6.x API change
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_GET_DISK_RO], [
+	AC_MSG_CHECKING([whether get_disk_ro() is available])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/blkdev.h>
+	],[
+		struct gendisk *disk = NULL;
+		(void) get_disk_ro(disk);
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_GET_DISK_RO, 1,
+		          [blk_disk_ro() is available])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])