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/rxvt/default.nix

@@ -0,0 +1,39 @@
+{ stdenv, fetchurl
+, pkgconfig, libtool
+, libX11, libXt, libXpm }:
+
+stdenv.mkDerivation rec {
+  pname = "rxvt";
+  version = "2.7.10";
+
+  src = fetchurl {
+    url = "mirror://sourceforge/rxvt/${pname}-${version}.tar.gz";
+    sha256 = "0jfl71gz3k7zh3kxdb8lxi06kajjnx7bq1rxjgk680l209jxask1";
+  };
+
+  nativeBuildInputs = [ pkgconfig ];
+  buildInputs = [ libtool libX11 libXt libXpm ];
+
+  configurePhase = ''
+    LIBTOOL=${libtool}/bin/libtool ./configure --prefix=$out --enable-everything --enable-smart-resize --enable-256-color
+  '';
+
+  meta = with stdenv.lib; {
+    homepage = "http://rxvt.sourceforge.net/";
+    description = "Colour vt102 terminal emulator with less features and lower memory consumption";
+    longDescription = ''
+      rxvt (acronym for our extended virtual terminal) is a terminal
+      emulator for the X Window System, originally written by Rob Nation
+      as an extended version of the older xvt terminal by John Bovey of
+      University of Kent. Mark Olesen extensively modified it later and
+      took over maintenance for several years.
+
+      rxvt is intended to be a slimmed-down alternate for xterm,
+      omitting some of its little-used features, like Tektronix 4014
+      emulation and toolkit-style configurability.
+    '';
+    maintainers = with maintainers; [ AndersonTorres ];
+    license = licenses.gpl2;
+    platforms = platforms.linux;
+  };
+}