Fixes build with >=GCC-4.3

http://bugs.gentoo.org/show_bug.cgi?id=292949

Patch written by Sebastian Luther <SebastianLuther@gmx.de>
--- a/pph.cc
+++ b/pph.cc
@@ -23,6 +23,7 @@
  */
 
 #include "pph.hh"
+#include <cstdio>
 #include <cmath>
 #include <snpfile/matrix.hh>
 using namespace BiRC::SNPFile;