* Unfortunately there isn't an easy registry key to check to see if the
2015-2019 redist that we need is installed. Instead we need to check the
major/minor version to see if it's at least 14.20.
* This is complicated by the fact that windows installer returns DWORD registry
values with an extra # but provides no built-in way to strip it so it can be
compared numerically. The solution we've used here is a custom vbscript
action, but apparently they are problematic. Worst case I believe this will
try to install the runtime when not necessary, which might require an
unnecessary reboot. Or alternatively it may misdetect the runtime as installed
but the large majority of people have a compatible redist so this isn't too
bad either.
* We don't really need to update the version, any VC 2015 version would do, and
it causes the installer to try to trigger a reboot if the CRT is in use, which
is quite likely.
* The AMD plugins e.g. don't have consistent incrementing versions, and in
general we don't care too much about version numbers or creation/modified
dates. We want the installer to always install the files it should.
baldurk