Fix bug in MapGetTileWorld and refactor

[hellworld111]

After analyzing the code, I have identified an issue with the MapGetTileWorld function where passing a negative x or y in the range of (-TILE_SIZE, 0) would return the first tile in the map instead of EMPTY. To address this issue, I have made a modification to the function where I immediately return EMPTY if x or y is negative. This not only fixes the problem but also simplifies the second condition on line 324, resulting in more efficient code.

Furthermore, upon reviewing the code, I noticed that the shift operator (>>) and TILE_SHIFT were being used unnecessarily for every call to MapGetTile. Given that this logic is already used inside of MapGetTileWorld, I replaced all instances of MapGetTile with MapGetTileWorld and removed the unnecessary shifting-related code. Consequently, the TILE_SHIFT variable was no longer required, allowing me to remove it and further streamline the code.

[abolinsky]

@raysan5

[raysan5]

@hellworld111 thanks for the review! Actually I haven't touched this code in many years, probably now I would write it in a completely different way.