Change: Limit memory allocations for each Squirrel instance

This can avoid out-of-memory situations due to single scripts using up the entire address space.
Instead, scripts that go above the maximum are killed.
The maximum is default 1 GB per script, but can be configured by a setting.

src/settings_gui.cpp

@@ -1757,6 +1757,7 @@ static SettingsContainer &GetSettingsTree()
 			{
 				npc->Add(new SettingEntry("script.settings_profile"));
 				npc->Add(new SettingEntry("script.script_max_opcode_till_suspend"));
+				npc->Add(new SettingEntry("script.script_max_memory_megabytes"));
 				npc->Add(new SettingEntry("difficulty.competitor_speed"));
 				npc->Add(new SettingEntry("ai.ai_in_multiplayer"));
 				npc->Add(new SettingEntry("ai.ai_disable_veh_train"));