Add nextstep port, courtesy of Ovidiu Predescu.

src/backend/port/nextstep/port-protos.h

@@ -0,0 +1,27 @@
+/*-------------------------------------------------------------------------
+ *
+ * port-protos.h--
+ *    port-specific prototypes for NeXT
+ *
+  
+-------------------------------------------------------------------------
+ */
+#ifndef PORT_PROTOS_H
+#define PORT_PROTOS_H
+
+#include "fmgr.h"			/* for func_ptr */
+#include "utils/dynamic_loader.h"
+
+void* next_dlopen(char* name);
+int next_dlclose(void* handle);
+void* next_dlsym (void *handle, char *symbol);
+char* next_dlerror(void);
+
+#define	pg_dlopen(f)	next_dlopen
+#define	pg_dlsym	next_dlsym
+#define	pg_dlclose	next_dlclose
+#define	pg_dlerror	next_dlerror
+
+/* port.c */
+
+#endif /* PORT_PROTOS_H */