Linux: fix build with system speex (1/2)

BUG=145507
TEST=none
Review URL: https://chromiumcodereview.appspot.com/11044009

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/speex@160092 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
diff --git a/speex.h b/speex.h
index 39591ce..c4b6da9 100644
--- a/speex.h
+++ b/speex.h
@@ -11,8 +11,12 @@
 
 #if defined(USE_SYSTEM_SPEEX)
 #include <speex/speex.h>
+#include <speex/speex_callbacks.h>
+#include <speex/speex_stereo.h>
 #else
 #include "third_party/speex/include/speex/speex.h"
+#include "third_party/speex/include/speex/speex_callbacks.h"
+#include "third_party/speex/include/speex/speex_stereo.h"
 #endif
 
 #endif  // THIRD_PARTY_SPEEX_SPEEX_H_