[amtk/master.nmake: 2/5] amtk-types.h: Add _AMTK_EXTERN

[Chun-wei Fan <fanchunwei src gnome org>]

commit 3506c432c53f7d06be5d8a08cc99e552fd5db2d1
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Apr 28 13:10:13 2020 +0800

    amtk-types.h: Add _AMTK_EXTERN
    
    We can use _AMTK_EXTERN later to decorate the public APIs in the headers so
    that we can override its definition in order to export these symbols via
    compiler directives, for compilers that do not support exporting by regex,
    etc.

 amtk/amtk-types.h | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/amtk/amtk-types.h b/amtk/amtk-types.h
index 4b7951d..5ed5873 100644
--- a/amtk/amtk-types.h
+++ b/amtk/amtk-types.h
@@ -36,6 +36,10 @@ typedef struct _AmtkApplicationWindow                AmtkApplicationWindow;
 typedef struct _AmtkFactory                    AmtkFactory;
 typedef struct _AmtkMenuShell                  AmtkMenuShell;
 
+#ifndef _AMTK_EXTERN
+#define _AMTK_EXTERN extern
+#endif
+
 G_END_DECLS
 
 #endif /* AMTK_TYPES_H */