Do not declare program_invocation_short_name because people can't make up their

mind what type it should be.

compat/getprogname.c

@@ -16,14 +16,14 @@
 
 #include <sys/types.h>
 
+#include <errno.h>
+
 #include "compat.h"
 
 #if defined(HAVE_PROGRAM_INVOCATION_SHORT_NAME)
 const char *
 getprogname(void)
 {
-	extern char	*program_invocation_short_name;
-
 	return (program_invocation_short_name);
 }
 #elif defined(HAVE___PROGNAME)