Add missing includes for strings.h

Several string functions were used without an explicit include.
This was discovered using an old version of GCC which warned about them;
these warnings are not seen with more recent compilers.

src/acl.c

@@ -5,6 +5,7 @@
 #include "client.h"
 
 #include <string.h>
+#include <strings.h>
 #include <evhttp.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>

src/client.c

@@ -9,6 +9,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 #include <errno.h>
 #include <hiredis/hiredis.h>

src/cmd.c

@@ -16,6 +16,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <hiredis/hiredis.h>
 #include <hiredis/async.h>
 #include <ctype.h>

src/conf.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <strings.h>
 #include <ctype.h>
 #include <arpa/inet.h>
 #include <unistd.h>

src/formats/json.c

@@ -5,6 +5,7 @@
 #include "client.h"
 
 #include <string.h>
+#include <strings.h>
 #include <hiredis/hiredis.h>
 #include <hiredis/async.h>
 

src/formats/msgpack.c

@@ -5,6 +5,7 @@
 #include "client.h"
 
 #include <string.h>
+#include <strings.h>
 #include <hiredis/hiredis.h>
 #include <hiredis/async.h>
 

src/http.c

@@ -5,6 +5,7 @@
 #include "slog.h"
 
 #include <string.h>
+#include <strings.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdio.h>