libgphoto: Switch to Github, allow building from repo.
libgphoto: Switch to Github, allow building from repo.

Github is where upstream's development happens now,
and building from repo makes adding patches and overriding the commit easier.

Also use pname+version, see #103997.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs