3357. [port] Add support for libxml2-2.8.x [RT #30440]

CHANGES

+3357.	[port]		Add support for libxml2-2.8.x [RT #30440]
+
 3356.	[bug]		Cap the TTL of signed RRsets when RRSIGs are 
 			approaching their expiry, so they don't remain
 			in caches after expiry. [RT #26429]

configure

@@ -23262,7 +23262,7 @@ case "$use_libxml2" in
 		;;
 	auto|yes)
 		case X`(xml2-config --version) 2>/dev/null` in
-		X2.[67].*)
+		X2.[678].*)
 			libxml2_libs=`xml2-config --libs`
 			libxml2_cflags=`xml2-config --cflags`
 			;;

configure.in

@@ -1326,7 +1326,7 @@ case "$use_libxml2" in
 		;;
 	auto|yes)
 		case X`(xml2-config --version) 2>/dev/null` in
-		X2.[[67]].*)
+		X2.[[678]].*)
 			libxml2_libs=`xml2-config --libs`
 			libxml2_cflags=`xml2-config --cflags`
 			;;