dns/dnsmasq-devel: Update to 2.81rc3 (from rc2).

Git changelog:

• 46bdfe6 2020-03-08 | Fix error in IPv6 prefix calculation. (HEAD -> master, tag: v2.81rc3, origin/master, origin/HEAD) [Petr Menšík]
• dded78b 2020-03-08 | Add DHCPv6 ntp-server (56) option handling. [Vladislav Grishenko]
• b594e8d 2020-03-06 | rfc3315: fix incorrect logical '&&' warning [Kevin Darbyshire-Bryant]
• 70c50ef 2020-03-06 | suppress non linux network unused var warnings [Kevin Darbyshire-Bryant]
• ea3c60a 2020-03-08 | Diverge error handling between *BSD and Linux. [Brad Smith]

Replace patch-Makefile by a $REINPLACE_CMD that support
nondefault lua versions 5.1 and 5.3, too.

Remove patch-src_rfc3315.c, same as b594e8d but written independently.