[netcurl] netcurl-6.1 soon to be merged into the master branch

[Tomas Tornevall]

Stable releases for netcurl v6.0 will, for now on, no longer be pushed
into the master repository. A new stable/6.0 has been created for
maintenance releases.

Version 6.1 is quite close to get a new tag and there's not many
compatibility issues left to take care of. The only bigger part that
awaits for 6.1 is the complementary network module.