[gegl] Issue #132: fix compilation for MSYS2.

[Jehan <jehanp src gnome org>]

commit 141a7aa76cd36143f624f06b1c43d2483945653c
Author: Jehan <jehan girinstud io>
Date:   Fri Mar 8 19:36:12 2019 +0100

    Issue #132: fix compilation for MSYS2.

 gegl/gegl-config.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/gegl/gegl-config.c b/gegl/gegl-config.c
index fd243e51e..65df46dd8 100644
--- a/gegl/gegl-config.c
+++ b/gegl/gegl-config.c
@@ -19,6 +19,9 @@
 #include "config.h"
 
 #include <string.h>
+#ifdef G_OS_WIN32
+#include <windows.h>
+#endif
 
 #include <glib-object.h>
 #include <glib/gprintf.h>