Excise DL_EXPORT from Include.

Thanks to Skip Montanaro and Kalle Svensson for the patches.
diff --git a/Include/pygetopt.h b/Include/pygetopt.h
index 9c74cbe..80908be 100644
--- a/Include/pygetopt.h
+++ b/Include/pygetopt.h
@@ -5,11 +5,11 @@
 extern "C" {
 #endif
 
-extern DL_IMPORT(int) _PyOS_opterr;
-extern DL_IMPORT(int) _PyOS_optind;
-extern DL_IMPORT(char *) _PyOS_optarg;
+PyAPI_DATA(int) _PyOS_opterr;
+PyAPI_DATA(int) _PyOS_optind;
+PyAPI_DATA(char *) _PyOS_optarg;
 
-DL_IMPORT(int) _PyOS_GetOpt(int argc, char **argv, char *optstring);
+PyAPI_FUNC(int) _PyOS_GetOpt(int argc, char **argv, char *optstring);
 
 #ifdef __cplusplus
 }