resolv: Remove internal and unused definitions from <resolv.h>

The RES_F_* constants are only used with the private _res._flags
member.  RES_EXHAUSTIVE is unused.  The removed function
declarations refer to functions not actually exported by glibc,
so they are unusable by applications.

resolv/res_query.c

@@ -74,6 +74,7 @@
 #include <errno.h>
 #include <netdb.h>
 #include <resolv.h>
+#include <resolv/resolv-internal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>