Fix build with gcc 4.6

diff -r 410f9e18a249 -r 915365c58758 build/linux/Makefile.linux
--- a/build/linux/Makefile.linux	Fri Oct 14 09:41:38 2011 +0100
+++ b/build/linux/Makefile.linux	Fri Oct 14 09:48:47 2011 +0100
@@ -1,5 +1,5 @@
 
-CFLAGS := -DNDEBUG -O3 -fno-exceptions -fPIC -ffast-math -msse -mfpmath=sse -ftree-vectorize -fomit-frame-pointer -DUSE_PTHREADS
+CFLAGS := -DNDEBUG -O3 -fno-exceptions -fPIC -ffast-math -msse -mfpmath=sse -ftree-vectorize -fomit-frame-pointer -DUSE_PTHREADS -I./include
 CXXFLAGS := $(CFLAGS)
 
 include build/general/Makefile.inc
diff -r 410f9e18a249 -r 915365c58758 dsp/tempotracking/DownBeat.h
--- a/dsp/tempotracking/DownBeat.h	Fri Oct 14 09:41:38 2011 +0100
+++ b/dsp/tempotracking/DownBeat.h	Fri Oct 14 09:48:47 2011 +0100
@@ -17,6 +17,7 @@
 #define DOWNBEAT_H
 
 #include <vector>
+#include <cstddef>
 
 #include "dsp/rateconversion/Decimator.h"
 
diff -r 410f9e18a249 -r 915365c58758 dsp/tempotracking/TempoTrackV2.h
--- a/dsp/tempotracking/TempoTrackV2.h	Fri Oct 14 09:41:38 2011 +0100
+++ b/dsp/tempotracking/TempoTrackV2.h	Fri Oct 14 09:48:47 2011 +0100
@@ -18,6 +18,7 @@
 #define TEMPOTRACKV2_H
 
 #include <vector>
+#include <cstddef>
 
 using std::vector;