[goffice] add missing header.

[Jean Bréfort <jbrefort src gnome org>]

commit 70a278d383e7def8a94f3b81185c02d907a54e92
Author: Jean Brefort <jean brefort normalesup org>
Date:   Fri Nov 6 15:55:57 2009 +0100

    add missing header.

 plugins/plot_pie/gog-pie.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/plugins/plot_pie/gog-pie.c b/plugins/plot_pie/gog-pie.c
index a6d0c6a..61f955d 100644
--- a/plugins/plot_pie/gog-pie.c
+++ b/plugins/plot_pie/gog-pie.c
@@ -35,6 +35,7 @@
 #include <glib/gi18n-lib.h>
 #include <gsf/gsf-impl-utils.h>
 #include <math.h>
+#include <string.h>
 
 static GObjectClass *ppe_parent_klass;