LUA_EnumLib optimizations for constant value access

• Constants are stored into _G after first use
• Made LUA_EvalMath's dedicated Lua state permanent so it can also benefit from these optimizations
• Tests show that time spent in game logic code improves by 10-20% when mods are loaded and player is idling on a map

Test build: (updated 2022-01-25) (based on next so be careful with your save files)

srb2win_lua-optimized-constants-2.exe