strigi: patch to compile on stdenv-updates (close #755)

This patch exports a class with STRIGI_EXPORT that wasn't exported
before.

pkgs/development/libraries/strigi/default.nix

@@ -20,6 +20,8 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ cmake pkgconfig perl ];
 
+  patches = [ ./export_bufferedstream.patch ];
+
   enableParallelBuilding = true;
 
   meta = {

pkgs/development/libraries/strigi/export_bufferedstream.patch

@@ -0,0 +1,12 @@
+diff -u -r strigi-0.7.8/libstreams/include/strigi/bufferedstream.h strigi-0.7.8_new/libstreams/include/strigi/bufferedstream.h
+--- strigi-0.7.8/libstreams/include/strigi/bufferedstream.h	2013-02-05 13:34:57.000000000 -0800
++++ strigi-0.7.8_new/libstreams/include/strigi/bufferedstream.h	2013-07-14 17:01:54.000000000 -0700
+@@ -34,7 +34,7 @@
+  * BufferedStream will do the rest.
+  */
+ template <class T>
+-class BufferedStream : public StreamBase<T> {
++class STRIGI_EXPORT BufferedStream : public StreamBase<T> {
+ private:
+     StreamBuffer<T> buffer;
+     bool finishedWritingToBuffer;