libroken: Fill in NI_NUMERICSCOPE as 0 if not defined.

This flag has defined by POSIX for years if not decades, but glibc
and Windows apparently still don't have it.

We will use it with getnameinfo, along with all other NI_NUMERICxxx
options, to minimize risk of network leaks with block_dns.

lib/roken/roken-common.h

@@ -251,6 +251,14 @@
 #define NI_NUMERICSERV	0x10
 #endif
 
+/*
+ * NI_NUMERICSCOPE is still missing from glibc as of 2024:
+ * https://sourceware.org/bugzilla/show_bug.cgi?id=14102
+ */
+#ifndef	NI_NUMERICSCOPE
+#define	NI_NUMERICSCOPE		0
+#endif
+
 /*
  * constants for getnameinfo
  */