[gimp] app: fix build error "‘memset’ was not declared in this scope".

[Jehan Pagès <jehanp src gnome org>]

commit 87b96116289b56d1410fab58ef28fd8def5fd571
Author: Jehan <jehan girinstud io>
Date:   Thu Apr 5 23:57:34 2018 +0200

    app: fix build error "‘memset’ was not declared in this scope".

 app/paint/gimpbrushcore-loops.cc |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/app/paint/gimpbrushcore-loops.cc b/app/paint/gimpbrushcore-loops.cc
index 87597e2..ecb01b7 100644
--- a/app/paint/gimpbrushcore-loops.cc
+++ b/app/paint/gimpbrushcore-loops.cc
@@ -17,6 +17,8 @@
 
 #include "config.h"
 
+#include <string.h>
+
 #include <gegl.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>