This looks way better than the first attempt:

 - both full and incremental upgrades are added for the existing v2
   boilerplate UDFs, regarding past versions: 4.0, 4.1, 4.1.1, and 4.2;

 - add boilerplate plus full/incremental upgrades for non-existing v2
   UDFs, regarding past versions: 4.0~beta1, 4.0~beta2, and 4.0~rc1;

 - add boilerplate UDFs for this release and the next two ones
   (emergency release and release candidate): 4.2.1, 4.2.2, 4.5~rc1;

 - minor edits (extra quotes around the version) for the existing v2
   boilerplate UDFs, regarding next versions: 4.3, 4.5 (presumably to
   avoid integer/string confusion).

This reverts commit 77fc5d4e.

The release process documentation being followed was buggy, let's start
over.

The new Upgrader, that'll be shipped in 4.2, will start looking
for upgrades via the v2 API. Until something strictly newer
than 4.2 is built and tested, there won't be upgrades available
regardless of the initially installed version.