Merge branch 'fix-missing-ipv6.h' into 'master'

Remove broken @ISC_IPV6_H@ placeholder from Makefile.in

See merge request isc-projects/bind9!720

lib/isc/include/isc/Makefile.in

@@ -24,7 +24,7 @@ HEADERS =	aes.h app.h assertions.h atomic.h backtrace.h base32.h base64.h \
 		errno.h error.h event.h eventclass.h \
 		file.h formatcheck.h fsaccess.h fuzz.h \
 		hash.h heap.h hex.h hmacmd5.h hmacsha.h ht.h httpd.h \
-		interfaceiter.h @ISC_IPV6_H@ iterated_hash.h \
+		interfaceiter.h iterated_hash.h \
 		json.h lang.h lex.h lfsr.h lib.h likely.h list.h log.h \
 		magic.h md5.h mem.h meminfo.h msgcat.h msgs.h mutexblock.h \
 		netaddr.h netscope.h nonce.h os.h parseint.h \