Add support for BSDI 5.x

Thanks to lidl@pix.net for the patch.
Bug #167375 r=cls,wtc

configure

@@ -4651,7 +4651,7 @@ fi
         _PEDANTIC=
     _IGNORE_LONG_LONG_WARNINGS=
     case $OS_RELEASE in
-	4.*)
+	4.*|5.*)
             STRIP="$STRIP -d"
             ;;
 	*)

configure.in

@@ -741,7 +741,7 @@ case "$target" in
     _PEDANTIC=
     _IGNORE_LONG_LONG_WARNINGS=
     case $OS_RELEASE in
-	4.*)
+	4.*|5.*)
             STRIP="$STRIP -d"
             ;;
 	*)