remove macros from header files

[treellama]

49f1d86 partially addresses this, but I'd also like to see the other similar #defines removed. Bonus points for adding accessors instead of extern std::vector<...>, and for removing the MAXIMUM_EFFECTS_PER_MAP macro as well. For example:

std::vector<effect_data>& get_effects();

or

effect_data* get_effects();
size_t get_maximum_effects();

and then

void resize_effects(size_t size);
void clear_effects();

Which would concentrate the logic in effects.cpp instead of spreading it across three files.