line clipping to avoid screen overflow

**loops and float points are expensive**, and I don't have enough geometry knowledge to do this without copying and pasting something ready, it would be interesting to have a method that wasn't so precise but was as fast as possible for the GBA's CPU.

* function `geoclip_line` in `src/geoclip.c`

https://github.com/gamelly/core-native-gba/blob/026a74e0c6efa5e6c231d1dbf7e3c0d96be5a236/src/geoclip.c#L42-L54

Start with geoclip_line in src/geoclip.c and inspect the linked implementation. Determine an approximate clipping approach that avoids loops and floating-point work while keeping lines within the GBA screen bounds. Done means the function clips overflowing lines and is suitable for the GBA CPU.

Written by the indexing model from the issue text.