Merge pull request #1531

9d1d3a45 portable serializer: use signed char for size (kenshi84)

external/boost/archive/portable_binary_iarchive.hpp

@@ -234,7 +234,7 @@ namespace boost { namespace archive {
 
 inline void 
 portable_binary_iarchive::load_impl(boost::intmax_t & l, char maxsize){
-    char size;
+    signed char size;
     l = 0;
     this->primitive_base_t::load(size);