altserver-linux: rename from alt-server / AltServer-Linux

- Make pname all lowercase—do not transform AltServer -> alt-server, but
  to altserver as the name already has hyphens elsewhere, and many other
  packages (including the example in nixpkgs manual) do this
- Change variable and dir names to match pname as deviation seems
  unnecessary here and only leads to confusion; this project is also a
  variation on AltServer-Windows, so keeping the “-linux” seems
  warranted

From https://nixos.org/manual/nixpkgs/unstable/#sec-package-naming:

> The pname and the version attribute must not contain uppercase letters
> e.g., "mplayer" instead of “MPlayer”`.

pkgs/tools/misc/altserver-linux/default.nix

@@ -6,7 +6,7 @@
 }:
 
 stdenv.mkDerivation (finalAttrs: {
-  pname = "AltServer-Linux";
+  pname = "altserver-linux";
   version = "0.0.5";
 
   src = fetchurl {

pkgs/top-level/all-packages.nix

@@ -262,7 +262,7 @@ with pkgs;
 
   alterx = callPackage ../tools/security/alterx { };
 
-  alt-server = callPackage ../tools/misc/alt-server { };
+  altserver-linux = callPackage ../tools/misc/altserver-linux { };
 
   asciicam = callPackage ../applications/video/asciicam { };