nutdrv_qx: fix 'megatec/old' and 'mustek' subdrivers' claim functions

Address, for 'megatec/old' and 'mustek' subdrivers, the same problem fixed in commit 720975f4de910b270ba705a7f2981c2ee33ca2eb for Q1-based ones (pull request #72):
- Make the claim function of 'megatec/old' and 'mustek' subdrivers not poll the UPS for 'vendor' informations as they are not really needed to set these protocols apart from the other ones (i.e. the 'status' poll is specific enough, at the time of writing).
- Move common 'light' claim function to nutdrv_qx_blazer-common.{c,h}.
- Update manual.
- Versioning.

This is, in my opinion, a better way to address the same problem than the one of #75, as it doesn't add a bunch of pretty useless subdrivers.