Move declaration of 'clnt_create()' NIS function to pyport.h, as it's

supposed to be declared in system include files (with a proper prototype.)
Should be moved to a platform-specific block if anyone finds out which
broken platforms need it :-)

Include/pyport.h

@@ -266,6 +266,9 @@ extern int lstat(const char *, struct stat *);
 extern int symlink(const char *, const char *);
 extern int fsync(int fd);
 
+/* From Modules/nismodule.c */
+CLIENT *clnt_create();
+
 #endif /* 0 */