Bug#1023632: Please package latest upstream version 4.0.0

[Simon McVittie]

On Mon, 07 Nov 2022 at 23:41:16 +0100, Michael Biebl wrote:
> The latest upstream version appears to be 4.0.0, so it would be nice to
> have this version in unstable / bookworm.

This is a parallel-installable API and ABI break which requires app
porting, so it should probably be packaged as a new src:gcr4 instead of
as a continuation of src:gcr.

    smcv