[libgd] build: Fix -Wimplicit-function-declaration warnings

[Christian Persch <chpe src gnome org>]

commit bbe712dc17e18e148c9ab0d2507e2e943097380b
Author: Christian Persch <chpe gnome org>
Date:   Wed Feb 13 12:32:41 2013 +0100

    build: Fix -Wimplicit-function-declaration warnings

 libgd/gd-stack.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/libgd/gd-stack.c b/libgd/gd-stack.c
index 79b844c..ac373c0 100644
--- a/libgd/gd-stack.c
+++ b/libgd/gd-stack.c
@@ -23,6 +23,7 @@
 #include <gtk/gtk.h>
 #include "gd-stack.h"
 #include <math.h>
+#include <string.h>
 
 #define FRAME_TIME_MSEC 17 /* 17 msec => 60 fps */