add NO_ADDRESS macro to netdb.h as an alias for NO_DATA

some applications expect it to be defined, despite the standard making
it impossible for it to ever be returned as a value distinct from
NO_DATA. since these macros are outside the scope of the current
standards, no special effort is made to hide NO_ADDRESS under
conditions where the others are exposed.

include/netdb.h

@@ -131,6 +131,7 @@ int *__h_errno_location(void);
 #define TRY_AGAIN      2
 #define NO_RECOVERY    3
 #define NO_DATA        4
+#define NO_ADDRESS     NO_DATA
 #endif
 
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)