nsis repackaging checkin in on trunk and branch

[Axel Hecht]

Hi,

bsmedberg checked in the nsis repackaging stuff and we're actually
seeing some green builds on trunk, and expecting the same on the branch
once cerberus cycles.

Thanks to Rob Strong, Benjamin, build and all who helped in getting that
3-headed beast wrestled down to its knees in the end.

The good news is, we're actually seeing build errors for installer files
in bad encodings, so from that point of view, we're better than the
xpinstall installer was.

For anything else, bang the installers and test them intensively and
compare the behaviour to the xpinstall installer that we used for 1.5.0.x.

Axel