ddns-scripts: add support for ipv64.net #21218

Job	Run time
Feeds Package Test Build / Test aarch64_generic	13m 40s
Feeds Package Test Build / Test arm_cortex-a15_neon-vfpv4	12m 43s
Feeds Package Test Build / Test arm_cortex-a9_vfpv3-d16	12m 57s
Feeds Package Test Build / Test i386_pentium-mmx	12m 58s
Feeds Package Test Build / Test mips_24kc	13m 18s
Feeds Package Test Build / Test mipsel_24kc	14m 10s
Feeds Package Test Build / Test powerpc_464fp	13m 58s
Feeds Package Test Build / Test powerpc_8548	13m 11s
Feeds Package Test Build / Test riscv64_riscv64	12m 9s
Feeds Package Test Build / Test x86_64	14m 9s
	2h 13m 13s

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