Each modified source file, before merging, must be formatted.
make code-format
This should be fine if you modified one of the files already present in the project, or added a file in a directory we already format, otherwise run:
./.custom-format.py -i file-that-you-have-created.c
Regarding the coding style, please follow the AFL style. No camel case at all and use the AFL's macros wherever possible (e.g. WARNF, FATAL, MAP_SIZE, ...).
Remember that AFLplusplus has to build and run on many platforms, so generalize your Makefiles (or your patches to our pre-existing Makefiles) to be as much generic as possible.