Update build system and packaging

Minimal changes required to integrate the SPL sources in to the
ZFS repository build infrastructure and packaging.

Build system and packaging:
  * Renamed SPL_* autoconf m4 macros to ZFS_*.
  * Removed redundant SPL_* autoconf m4 macros.
  * Updated the RPM spec files to remove SPL package dependency.
  * The zfs package obsoletes the spl package, and the zfs-kmod
    package obsoletes the spl-kmod package.
  * The zfs-kmod-devel* packages were updated to add compatibility
    symlinks under /usr/src/spl-x.y.z until all dependent packages
    can be updated.  They will be removed in a future release.
  * Updated copy-builtin script for in-kernel builds.
  * Updated DKMS package to include the spl.ko.
  * Updated stale AUTHORS file to include all contributors.
  * Updated stale COPYRIGHT and included the SPL as an exception.
  * Renamed README.markdown to README.md
  * Renamed OPENSOLARIS.LICENSE to LICENSE.
  * Renamed DISCLAIMER to NOTICE.

Required code changes:
  * Removed redundant HAVE_SPL macro.
  * Removed _BOOT from nvpairs since it doesn't apply for Linux.
  * Initial header cleanup (removal of empty headers, refactoring).
  * Remove SPL repository clone/build from zimport.sh.
  * Use of DEFINE_RATELIMIT_STATE and DEFINE_SPINLOCK removed due
    to build issues when forcing C99 compilation.
  * Replaced legacy ACCESS_ONCE with READ_ONCE.
  * Include needed headers for `current` and `EXPORT_SYMBOL`.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
TEST_ZIMPORT_SKIP="yes"
Closes #7556

module/zfs/zfs_vfsops.c

@@ -27,17 +27,13 @@
 
 #include <sys/types.h>
 #include <sys/param.h>
-#include <sys/systm.h>
 #include <sys/sysmacros.h>
 #include <sys/kmem.h>
 #include <sys/pathname.h>
 #include <sys/vnode.h>
 #include <sys/vfs.h>
-#include <sys/vfs_opreg.h>
 #include <sys/mntent.h>
-#include <sys/mount.h>
 #include <sys/cmn_err.h>
-#include "fs/fs_subr.h"
 #include <sys/zfs_znode.h>
 #include <sys/zfs_vnops.h>
 #include <sys/zfs_dir.h>
@@ -51,18 +47,12 @@
 #include <sys/zap.h>
 #include <sys/sa.h>
 #include <sys/sa_impl.h>
-#include <sys/varargs.h>
 #include <sys/policy.h>
 #include <sys/atomic.h>
-#include <sys/mkdev.h>
-#include <sys/modctl.h>
-#include <sys/refstr.h>
 #include <sys/zfs_ioctl.h>
 #include <sys/zfs_ctldir.h>
 #include <sys/zfs_fuid.h>
-#include <sys/bootconf.h>
 #include <sys/sunddi.h>
-#include <sys/dnlc.h>
 #include <sys/dmu_objset.h>
 #include <sys/spa_boot.h>
 #include <sys/zpl.h>
@@ -2341,7 +2331,7 @@ zfs_fini(void)
 	zfsctl_fini();
 }
 
-#if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_KERNEL)
 EXPORT_SYMBOL(zfs_suspend_fs);
 EXPORT_SYMBOL(zfs_resume_fs);
 EXPORT_SYMBOL(zfs_userspace_one);