Log Message:
Update Unix VM to 3.6-3, and default image to 3.6-5429.  Many improvements
and enhancements since 3.0. Notably, display and sound plugins can now be
selected at run-time, and support is added for character set conversion.
This package also contains a driver for NetBSD native audio, by yours truly.

OSS audio requires a newer interface than NetBSD emulation supports, so that
doesn't build anymore on NetBSD, though it may with third party drivers. NAS
builds on NetBSD, but doesn't work. There are new display drivers which build
selectively on linux and MacOS, and a new audio driver for MacOS. I'm marking
this package ONLY_FOR_PLATFORM=NetBSD-*-*, though, mainly because the static
PLIST that the package presently has can't reflect any of that.

This closes PR pkg/17950.