The new bash-completion support in NixOS doesn't require this patch anymore.
Besides, the patch was insufficient for most purposes anyway: Bash completion
modules are spread out over all user profiles listed in $NIX_PROFILES (plus the
current-system profile), so getting full support for all installed modules
requires support for more than one "bash_completion.d" directory anyway.
Please note that this update changes the directory structure quite a bit. In
particular, the file "/etc/bash_completion" no longer exists, which means that
shell code which relies on that path must be updated. I'll commit appropriate
changes for NixOS in a moment.
