aliases: document avoiding them within nixpkgs better

lib: self: super:

### Deprecated aliases - for backward compatibility

### Please maintain this list in ASCIIbetical ordering.

### Hint: the "sections" are delimited by ### <letter> ###

# These aliases should not be used within nixpkgs, but exist to improve

# backward compatibility in projects outside of nixpkgs. See the

# documentation for the `allowAliases` option for more background.

# A script to convert old aliases to throws and remove old

# throws can be found in './maintainers/scripts/remove-old-aliases.py'.

# Add 'preserve, reason: reason why' after the date if the alias should not be removed.

# Try to keep them to a minimum.

# valid examples of what to preserve:

#   distro aliases such as:

#     debian-package-name -> nixos-package-name

with self;

let

      aliases;

in

### Deprecated aliases - for backward compatibility

### Please maintain this list in ASCIIbetical ordering.

### Hint: the "sections" are delimited by ### <letter> ###

# A script to convert old aliases to throws and remove old

# throws can be found in './maintainers/scripts/remove-old-aliases.py'.

# Add 'preserve, reason: reason why' after the date if the alias should not be removed.

# Try to keep them to a minimum.

# valid examples of what to preserve:

#   distro aliases such as:

#     debian-package-name -> nixos-package-name

mapAliases ({

  # Added 2018-07-16 preserve, reason: forceSystem should not be used directly in Nixpkgs.

  forceSystem = system: _: