dns/nsd: Fix missing _t to _type conversion for disable-radix-tree option

• Noting NSD changelog, recent update renamed _t typedefs because POSIX reserves them. The 4.1.15 update missed a few conversion.
• Unbreak RADIXTREE. No PORTREVISION change as port would not have built.

PR: 217640
Reported by: Max Kostikov <max@kostikov.co>
Submitted by: w.schwarzenfeld@utanet.at (the suggested diff)

		jaap@NLnetLabs.nl (maintainer - the port patch)

Obtained from: nsd svn r4741