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/unicode/u8_textprep.c

@@ -36,18 +36,13 @@
  */
 
 #include <sys/types.h>
-#ifdef	_KERNEL
+#include <sys/strings.h>
 #include <sys/param.h>
 #include <sys/sysmacros.h>
-#include <sys/systm.h>
 #include <sys/debug.h>
 #include <sys/kmem.h>
-#include <sys/ddi.h>
 #include <sys/sunddi.h>
-#else
 #include <sys/u8_textprep.h>
-#include <strings.h>
-#endif	/* _KERNEL */
 #include <sys/byteorder.h>
 #include <sys/errno.h>
 #include <sys/u8_textprep_data.h>
@@ -2130,7 +2125,7 @@ u8_textprep_str(char *inarray, size_t *inlen, char *outarray, size_t *outlen,
 	return (ret_val);
 }
 
-#if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_KERNEL)
 static int __init
 unicode_init(void)
 {

module/unicode/uconv.c

@@ -38,7 +38,6 @@
 #ifdef	_KERNEL
 #include <sys/param.h>
 #include <sys/sysmacros.h>
-#include <sys/systm.h>
 #include <sys/debug.h>
 #include <sys/kmem.h>
 #include <sys/sunddi.h>
@@ -854,7 +853,7 @@ uconv_u8tou32(const uchar_t *u8s, size_t *utf8len,
 	return (0);
 }
 
-#if defined(_KERNEL) && defined(HAVE_SPL)
+#if defined(_KERNEL)
 EXPORT_SYMBOL(uconv_u16tou32);
 EXPORT_SYMBOL(uconv_u16tou8);
 EXPORT_SYMBOL(uconv_u32tou16);