Switch the main dev branch back to 'master'

Switch the main dev branch back to 'master'

Previously the idea was to have two dev branches - one for "the crowd", and
another one for the rel manager to do periodic squashes, merges, cleanups etc.
This worked rather well for about 1.5 years, but with the primary architect
outgoing it can't be sustained, and only serves to confuse everyone.

Thus a fast forward with a mini-merge of master up to the tip of current/blead
and continuing pushes to master alone from there on. Not yet deleting the old
'current/blead' and 'current/for_cpan_index' branches, as it affects PR states
due to useless "smarts" in the github logic.