perf tools: Remove string.h from util.h

Not needed in this header, added to the places that need strdup,
strcmp and a few other prototypes.

Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/comm.c

···
 #include <errno.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 #include <linux/refcount.h>
 
 struct comm_str {

tools/perf/util/namespaces.c

···
 #include "event.h"
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 
 struct namespaces *namespaces__new(struct namespaces_event *event)
 {

tools/perf/util/util.h

···
 #include <stddef.h>
 #include <stdlib.h>
 #include <stdarg.h>
-#include <string.h>
 #include <sys/wait.h>
 #include <poll.h>
 #include <linux/types.h>

tools/perf/util/xyarray.c

···
 #include "xyarray.h"
 #include "util.h"
+#include <stdlib.h>
+#include <string.h>
 
 struct xyarray *xyarray__new(int xlen, int ylen, size_t entry_size)
 {