A directory-category for terminal emulators

This is a mostly cosmetical commit, in the sense it doesn't change the contents
of any package, but reorganizes the overall Nixpkgs expressions.

Terminal emulators are an ubiquitous tool for any Unix user; even the beginners
are routinely familiarized to it. And, manifestly, there are many
implementations of terminal emulators out there, from those traditionally made
in C and C++ to those written in Haskell and Go.

Terminal emulators deserve more highlight. This commit does that by creating a
category for them.

pkgs/applications/terminal-emulators/microcom/default.nix

@@ -0,0 +1,29 @@
+{ stdenv,
+  lib,
+  fetchFromGitHub,
+  readline,
+  autoreconfHook }:
+
+stdenv.mkDerivation rec {
+  pname = "microcom";
+  version = "2019.01.0";
+
+  src = fetchFromGitHub {
+    owner = "pengutronix";
+    repo = pname;
+    rev = "v${version}";
+    sha256 = "056v28hvagnzns6p8i3bq8609k82d3w1ab2lab5dr4cdfwhs4pqj";
+  };
+
+  nativeBuildInputs = [ autoreconfHook ];
+  buildInputs = [ readline ];
+
+  meta = with lib; {
+    description = "A minimalistic terminal program for communicating
+    with devices over a serial connection";
+    inherit (src.meta) homepage;
+    license = licenses.gpl2;
+    maintainers = with maintainers; [ emantor ];
+    platforms = with platforms; linux;
+  };
+}