Decompile 2 functions in Source/Resource/World/GroundResource.cpp, Source/Resource/World/GroundResource.h

Batch #1185 by eAthena: 0 byte-identical, 2 confirmed by peer review.

- fn_07909 GroundLegacyLightmap::Decode: logic confirmed by peer review (annotation added to existing code)
- fn_07910 CGndRes::Lightmap: logic confirmed by peer review (already on main)

Reviewed-by: ragnarok-clanker

Source/Resource/World/GroundResource.cpp

@@ -129,6 +129,7 @@ void CGndRes::Unload() {
 }
 
 // OFFSET: 0x0074E4B0
+// FUNCTION: fn_07909
 void GroundLegacyLightmap::Decode(unsigned char* output) const {
   int pixel = 0;