fvwm: add readline, fix man build, refactor fetch

The fvwm.1 man page was missing for the standard build of fvwm. While
digging, I also noticed that readline was not included (which, when
included, makes FvwmConsole much more pleasant to use). Based on those
two items, the following changes are in this commit.

- Add libxslt for xsltproc tool, used in building documentation

- Explicitly direct creation of man pages (prior to this change, the
  fvwm.1 man page was not built)

- Explicitly direct HTML documentation not to be built

- Add readline for use in FvwmConsole

While changing things in this package anyway, I made the following
adjustments.

- Use fetchFromGitHub instead of fetchUrl

- Reformat with nixfmt

pkgs/applications/window-managers/fvwm/default.nix

@@ -1,27 +1,37 @@
-{ gestures ? false
-, lib, stdenv, fetchurl, pkg-config
-, cairo, fontconfig, freetype, libXft, libXcursor, libXinerama
-, libXpm, libXt, librsvg, libpng, fribidi, perl
-, libstroke ? null
-}:
-
-assert gestures -> libstroke != null;
+{ autoreconfHook, enableGestures ? false, lib, stdenv, fetchFromGitHub
+, pkg-config, cairo, fontconfig, freetype, libXft, libXcursor, libXinerama
+, libXpm, libXt, librsvg, libpng, fribidi, perl, libstroke, readline, libxslt }:
 
 stdenv.mkDerivation rec {
   pname = "fvwm";
   version = "2.6.9";
 
-  src = fetchurl {
-    url = "https://github.com/fvwmorg/fvwm/releases/download/${version}/${pname}-${version}.tar.gz";
-    sha256 = "1bliqcnap7vb3m2rn8wvxyfhbf35h9x34s41fl4301yhrkrlrihv";
+  src = fetchFromGitHub {
+    owner = "fvwmorg";
+    repo = pname;
+    rev = version;
+    sha256 = "14jwckhikc9n4h93m00pzjs7xm2j0dcsyzv3q5vbcnknp6p4w5dh";
   };
 
-  nativeBuildInputs = [ pkg-config ];
+  nativeBuildInputs = [ autoreconfHook pkg-config ];
   buildInputs = [
-    cairo fontconfig freetype
-    libXft libXcursor libXinerama libXpm libXt
-    librsvg libpng fribidi perl
-  ] ++ lib.optional gestures libstroke;
+    cairo
+    fontconfig
+    freetype
+    libXft
+    libXcursor
+    libXinerama
+    libXpm
+    libXt
+    librsvg
+    libpng
+    fribidi
+    perl
+    readline
+    libxslt
+  ] ++ lib.optional enableGestures libstroke;
+
+  configureFlags = [ "--enable-mandoc" "--disable-htmldoc" ];
 
   meta = {
     homepage = "http://fvwm.org";