example interface and C plugin

tests/examples/example_plugin.c

@@ -0,0 +1,44 @@
+#include <stdio.h>
+
+#include "hello_interface.h"
+
+int myopen(void)
+{
+  printf("opened\n");
+}
+
+int myclose(void);
+{
+  printf("closed\n");
+}
+
+int hallo(void)
+{
+  printf("Hallo Welt!\n");
+}
+
+int tschuess(const char* m)
+{
+  printf("Tschues %s\n", m);
+}
+
+int hello(void);
+{
+  printf("Hello world!\n");
+}
+
+int bye(const char* m)
+{
+  printf("bye %s\n", m);
+
+}
+
+CINELERRA_INTERFACE_IMPLEMENT(hello, 1, german, myopen, myclose,
+                              CINELERRA_INTERFACE_FUNC(hello, hallo),
+                              CINELERRA_INTERFACE_FUNC(goodbye, tschuess)
+                              );
+
+CINELERRA_INTERFACE_IMPLEMENT(hello, 1, english, myopen, myclose,
+                              CINELERRA_INTERFACE_FUNC(hello, hello),
+                              CINELERRA_INTERFACE_FUNC(goodbye, bye)
+                              );

tests/examples/hello_interface.h

@@ -0,0 +1,6 @@
+#include "plugin.h"
+
+CINELERRA_INTERFACE(hello, 1,
+                    CINELERRA_INTERFACE_PROTO(void, hello, (void)),
+                    CINELERRA_INTERFACE_PROTO(void, goodbye, (const char*)),
+                    );