[sysprof] add string.h

[Christian Hergert <chergert src gnome org>]

commit 6083e98affb2df38596bb2caf310dd0114ed1519
Author: Christian Hergert <chergert redhat com>
Date:   Mon May 13 00:12:24 2019 -0700

    add string.h

 src/libsysprof-ui/sysprof-marks-model.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/libsysprof-ui/sysprof-marks-model.c b/src/libsysprof-ui/sysprof-marks-model.c
index 16a675d..139c8ea 100644
--- a/src/libsysprof-ui/sysprof-marks-model.c
+++ b/src/libsysprof-ui/sysprof-marks-model.c
@@ -22,6 +22,8 @@
 
 #include "config.h"
 
+#include <string.h>
+
 #include "sysprof-marks-model.h"
 
 struct _SysprofMarksModel