Performance improvements of some lua APIs

[Helyos96]

• Use lua_tonumberx/lua_tointegerx instead of separated calls like lua_isnumber/lua_tonumber
• Avoid evaluating luaL_typename in the asserts when there is no need (these were always evaluated even when the assert didn't trigger)
• Drop the sscanf() call in ReadColorEscape
• Avoid calling IsColorEscape twice for ReadColorEscape

While profiling SimpleGraphics, I saw that l_DrawImage, l_DrawImageQuad and l_SetDrawColor were very consuming while in tree view (not very surprising).

I found a few improvements to do, which mostly revolve around eliminating some calls to luaJit and dropping a costly sscanf().

Profiling before:

And after:

The most obvious gain is l_SetDrawColor with sscanf being dropped. The l_DrawImage functions saw fewer gains but still less time spent in lua functions, especially the calls to lua_type went much lower.

Looking at task manager, PoB went from ~6.5% (maxing out one logical core) to ~5.9%. It could be that in doing so I gained a few fps, which skewed a bit the profiling data since these functions got to be called more.

[zao]

The transformations look valid from reading the code and it builds locally.
I didn't run any performance tests but the reasoning here seems sound.