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_ioctl.c

@@ -144,12 +144,8 @@
 #include <sys/param.h>
 #include <sys/errno.h>
 #include <sys/uio.h>
-#include <sys/buf.h>
-#include <sys/modctl.h>
-#include <sys/open.h>
 #include <sys/file.h>
 #include <sys/kmem.h>
-#include <sys/conf.h>
 #include <sys/cmn_err.h>
 #include <sys/stat.h>
 #include <sys/zfs_ioctl.h>
@@ -160,7 +156,6 @@
 #include <sys/spa_impl.h>
 #include <sys/vdev.h>
 #include <sys/vdev_impl.h>
-#include <sys/priv_impl.h>
 #include <sys/dmu.h>
 #include <sys/dsl_dir.h>
 #include <sys/dsl_dataset.h>
@@ -169,14 +164,11 @@
 #include <sys/dmu_objset.h>
 #include <sys/dmu_impl.h>
 #include <sys/dmu_tx.h>
-#include <sys/ddi.h>
 #include <sys/sunddi.h>
-#include <sys/sunldi.h>
 #include <sys/policy.h>
 #include <sys/zone.h>
 #include <sys/nvpair.h>
 #include <sys/pathname.h>
-#include <sys/mount.h>
 #include <sys/sdt.h>
 #include <sys/fs/zfs.h>
 #include <sys/zfs_ctldir.h>
@@ -184,7 +176,6 @@
 #include <sys/zfs_onexit.h>
 #include <sys/zvol.h>
 #include <sys/dsl_scan.h>
-#include <sharefs/share.h>
 #include <sys/fm/util.h>
 #include <sys/dsl_crypt.h>
 
@@ -7115,7 +7106,7 @@ _fini(void)
 	    ZFS_META_VERSION, ZFS_META_RELEASE, ZFS_DEBUG_STR);
 }
 
-#ifdef HAVE_SPL
+#if defined(_KERNEL)
 module_init(_init);
 module_exit(_fini);
 
@@ -7123,4 +7114,4 @@ MODULE_DESCRIPTION("ZFS");
 MODULE_AUTHOR(ZFS_META_AUTHOR);
 MODULE_LICENSE(ZFS_META_LICENSE);
 MODULE_VERSION(ZFS_META_VERSION "-" ZFS_META_RELEASE);
-#endif /* HAVE_SPL */
+#endif