Adds missing imports to fix compilation errors

omigen_py/py_gen.cpp

@@ -5,6 +5,7 @@
 
 #include <pal/dir.h>
 #include <base/types.h>
+#include <algorithm>
 #include <cassert>
 #include <cctype>
 #include <cstdlib>

test/socket_wrapper_test.cpp

@@ -4,6 +4,7 @@
 
 
 #include <cstdlib>
+#include <cstring>
 #include <errno.h>
 #include <signal.h>
 #include <socket_wrapper.hpp>

test/test_helper.cpp

@@ -3,6 +3,7 @@
 #include "test_helper.hpp"
 
 
+#include <cstdlib>
 #include <iostream>
 
 

test/test_helper.hpp

@@ -4,6 +4,7 @@
 #define INCLUDED_TEST_HELPER_HPP
 
 
+#include <cstdlib>
 #include <iosfwd>
 #include <iostream>
 #include <utility>