Cleaned up the mapflag system (#2943)

* Created setter and getter functions.
* Adjusted all calls to use these functions.
* Converted mapflags to C++ map container.
* Converted drop_list to vector.
* Converted skill_damage ERS into vector and increased limit from UINT8 to UINT16.
* Cleaned up several functions to be more dynamic to reduce redundancy that was all over the place.
* Renamed nosumstarmiracle to nosunmoonstarmiracle.
* Adjusted skill_damage mapflag to use proper defined constants.
* Refactored map index into a vector.
Thanks to @Lemongrass3110 for a lot of help and @secretdataz!

src/map/instance.cpp

@@ -25,8 +25,6 @@
 
 #define INSTANCE_INTERVAL	60000	// Interval used to check when an instance is to be destroyed (ms)
 
-int instance_start = 0; // To keep the last index + 1 of normal map inserted in the map[ARRAY]
-
 struct instance_data instance_data[MAX_INSTANCE_DATA];
 struct eri *instance_maps_ers = NULL; ///< Array of maps per instance