gphoto2: Include upstream type cast fix as patch

The patch added in this commit contains a fix that was done upstream in commit
366930ccc1

pkgs/applications/misc/gphoto2/add-type-casts.diff

@@ -0,0 +1,21 @@
+diff --git a/gphoto2/main.c b/gphoto2/main.c
+index 2bf5964..cd84467 100644
+--- a/gphoto2/main.c
++++ b/gphoto2/main.c
+@@ -1215,14 +1215,14 @@ start_timeout_func (Camera *camera, unsigned int timeout,
+ 
+ 	pthread_create (&tid, NULL, thread_func, td);
+ 
+-	return (tid);
++	return (unsigned int)tid;
+ }
+ 
+ static void
+ stop_timeout_func (Camera __unused__ *camera, unsigned int id,
+ 		   void __unused__ *data)
+ {
+-	pthread_t tid = id;
++	pthread_t tid = (pthread_t)id;
+ 
+ 	pthread_cancel (tid);
+ 	pthread_join (tid, NULL);

pkgs/applications/misc/gphoto2/default.nix

@@ -1,11 +1,16 @@
-{ lib, stdenv, fetchFromGitHub, autoreconfHook, pkg-config
-, gettext
-, libexif
-, libgphoto2
-, libjpeg
-, libtool
-, popt
-, readline
+{
+  lib,
+  stdenv,
+  fetchFromGitHub,
+  autoreconfHook,
+  pkg-config,
+  gettext,
+  libexif,
+  libgphoto2,
+  libjpeg,
+  libtool,
+  popt,
+  readline,
 }:
 
 stdenv.mkDerivation rec {
@@ -19,6 +24,8 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-t5EnM4WaDbOTPM+rJW+hQxBgNErnnZEN9lZvxTKoDhA=";
   };
 
+  patches = [ ./add-type-casts.diff ];
+
   nativeBuildInputs = [
     autoreconfHook
     pkg-config