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_vnops.c

@@ -33,11 +33,8 @@
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/time.h>
-#include <sys/systm.h>
 #include <sys/sysmacros.h>
-#include <sys/resource.h>
 #include <sys/vfs.h>
-#include <sys/vfs_opreg.h>
 #include <sys/file.h>
 #include <sys/stat.h>
 #include <sys/kmem.h>
@@ -45,11 +42,9 @@
 #include <sys/uio.h>
 #include <sys/vmsystm.h>
 #include <sys/atomic.h>
-#include <vm/pvn.h>
 #include <sys/pathname.h>
 #include <sys/cmn_err.h>
 #include <sys/errno.h>
-#include <sys/unistd.h>
 #include <sys/zfs_dir.h>
 #include <sys/zfs_acl.h>
 #include <sys/zfs_ioctl.h>
@@ -61,22 +56,16 @@
 #include <sys/dbuf.h>
 #include <sys/zap.h>
 #include <sys/sa.h>
-#include <sys/dirent.h>
 #include <sys/policy.h>
 #include <sys/sunddi.h>
 #include <sys/sid.h>
 #include <sys/mode.h>
-#include "fs/fs_subr.h"
 #include <sys/zfs_ctldir.h>
 #include <sys/zfs_fuid.h>
 #include <sys/zfs_sa.h>
 #include <sys/zfs_vnops.h>
-#include <sys/dnlc.h>
 #include <sys/zfs_rlock.h>
-#include <sys/extdirent.h>
-#include <sys/kidmap.h>
 #include <sys/cred.h>
-#include <sys/attr.h>
 #include <sys/zpl.h>
 #include <sys/zil.h>
 #include <sys/sa_impl.h>
@@ -5234,7 +5223,7 @@ zfs_retzcbuf(struct inode *ip, xuio_t *xuio, cred_t *cr)
 }
 #endif /* HAVE_UIO_ZEROCOPY */
 
-#if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_KERNEL)
 EXPORT_SYMBOL(zfs_open);
 EXPORT_SYMBOL(zfs_close);
 EXPORT_SYMBOL(zfs_read);