So, it appears that once our dialog is created, the DialogBox windowproc
is nuked. So, to hack around this, any errors that occur while it is open
are cached and reported out after we close everything down. It sucks, but
it works. I blame Microsoft.
This is the crowning feature: the whole point of this exercise. You can
now update redists from the client launcher itself. To activate this
functionality, you will need to flag the file 0x10 in the manifest. I
recommend listing your redists in the patcher manifests.