Compile cityhash code into libzfs

Make the cityhash code compile into libzfs, in preparation for the new
"zstream" command.

Reviewed-by: Paul Dagnelie <pcd@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #10152

include/sys/Makefile.am

@@ -14,7 +14,6 @@ COMMON_H = \
 	$(top_srcdir)/include/sys/bptree.h \
 	$(top_srcdir)/include/sys/btree.h \
 	$(top_srcdir)/include/sys/bqueue.h \
-	$(top_srcdir)/include/sys/cityhash.h \
 	$(top_srcdir)/include/sys/dataset_kstats.h \
 	$(top_srcdir)/include/sys/dbuf.h \
 	$(top_srcdir)/include/sys/ddt.h \

include/sys/cityhash.h

@@ -1,41 +0,0 @@
-// Copyright (c) 2011 Google, Inc.
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in
-// all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-// THE SOFTWARE.
-
-
-/*
- * Copyright (c) 2017 by Delphix. All rights reserved.
- */
-
-#ifndef	_SYS_CITYHASH_H
-#define	_SYS_CITYHASH_H
-
-#include <sys/zfs_context.h>
-
-#ifdef	__cplusplus
-extern "C" {
-#endif
-
-uint64_t cityhash4(uint64_t, uint64_t, uint64_t, uint64_t);
-
-#ifdef	__cplusplus
-}
-#endif
-
-#endif	/* _SYS_CITYHASH_H */