New gcc compilation fixes

libs/ecs/source/entity_container.cpp

@@ -16,7 +16,7 @@ namespace psemek::ecs
 
 	entity_accessor entity_container::get(entity_handle const & entity)
 	{
-		auto const & data = entity_list_.get_entities()[entity.id];
+		auto const data = entity_list_.get_entities()[entity.id];
 		return {data.table, data.row};
 	}
 

libs/gfx/include/psemek/gfx/attribs.hpp

@@ -10,6 +10,7 @@
 #include <vector>
 #include <optional>
 #include <array>
+#include <cstdint>
 
 namespace psemek::gfx
 {

libs/ml/include/psemek/ml/neural_net/activation.hpp

@@ -5,6 +5,7 @@
 #include <cmath>
 #include <algorithm>
 #include <exception>
+#include <cstdint>
 
 namespace psemek::ml
 {

libs/phys/include/psemek/phys/engine_2d.hpp

@@ -8,6 +8,7 @@
 
 #include <memory>
 #include <variant>
+#include <cstdint>
 
 namespace psemek::phys2d
 {

libs/phys/include/psemek/phys/engine_3d.hpp

@@ -8,6 +8,7 @@
 #include <psemek/util/pimpl.hpp>
 
 #include <variant>
+#include <cstdint>
 
 namespace psemek::phys3d
 {