speexdsp: fix integer types not being included

Description in comments of https://aur.archlinux.org/packages/retroshare/
I'm not sure why their conditionals don't work, but this fix should be safe.

/cc maintainer @wkennington.

pkgs/development/libraries/speexdsp/default.nix

@@ -9,6 +9,7 @@ stdenv.mkDerivation rec {
   };
 
   patches = [ ./build-fix.patch ];
+  postPatch = "sed '3i#include <stdint.h>' -i ./include/speex/speexdsp_config_types.h.in";
 
   nativeBuildInputs = [ autoreconfHook pkgconfig ];
   buildInputs = [ fftw ];