Remove a bunch of unreferenced files

Plus a small number of obsolete packages (like old versions of qemu).

pkgs/applications/graphics/darktable/libpng-15.patch

@@ -1,22 +0,0 @@
-commit 5803d31ae7704e0349821dcc20a94a1cddda69f1
-Author: Tim Harder <radhermit@gmail.com>
-Date:   Wed Sep 21 14:13:55 2011 -0700
-
-    Fix build with libpng-1.5
-    
-    Explicitly include the zlib.h header for the Z_BEST_COMPRESSION and
-    Z_DEFAULT_STRATEGY macros since >=libpng-1.5 doesn't pull it in anymore
-    via the png.h header.
-
-diff --git a/src/imageio/format/png.c b/src/imageio/format/png.c
-index 40c7d48..c7be566 100644
---- a/src/imageio/format/png.c
-+++ b/src/imageio/format/png.c
-@@ -28,6 +28,7 @@
- #include <stdio.h>
- #include <png.h>
- #include <inttypes.h>
-+#include <zlib.h>
- 
- DT_MODULE(1)
-