Fix build with newer Boost.

Taken from upstream:

  https://github.com/fifengine/fifengine/commit/8072f18a9bf4e75c3e1b197b6ccda11e82954460

diff --git a/engine/core/vfs/zip/zipnode.cpp b/engine/core/vfs/zip/zipnode.cpp
--- a/engine/core/vfs/zip/zipnode.cpp
+++ b/engine/core/vfs/zip/zipnode.cpp
@@ -28,6 +28,7 @@
 #include "vfs/fife_boost_filesystem.h"
 
 #include "zipnode.h"
+#include <algorithm>
 
 namespace {
     /** helper function to find a value in a ZipNodeContainer
