build: add missing includes

detected under libstdc++ from gcc-6.0

crypto/arc4.cpp

@@ -17,6 +17,7 @@
 #include "arc4.hpp"
 
 #include <algorithm>
+#include <numeric>
 
 using util::crypto::ARC4;
 

extent.cpp

@@ -21,6 +21,7 @@
 #include "./stream.hpp"
 
 #include <cmath>
+#include <numeric>
 
 using util::extent;
 using util::extent_range;

geom/aabb.ipp

@@ -22,6 +22,7 @@
 
 #include "sample.hpp"
 
+#include <random>
 
 namespace util { namespace geom {
     template <size_t S, typename T, typename G>