Add missing numeric includes in files using std::accumulate()

Reported-By: Helmut Grohne on IRC

apt-pkg/acquire-item.cc

@@ -45,6 +45,7 @@
 #include <stdio.h>
 #include <ctime>
 #include <sstream>
+#include <numeric>
 
 #include <apti18n.h>
 									/*}}}*/

apt-pkg/deb/dpkgpm.cc

@@ -49,6 +49,7 @@
 #include <utility>
 #include <vector>
 #include <sstream>
+#include <numeric>
 
 #include <apti18n.h>
 									/*}}}*/