accept most changes that only remove includes / forward declarations (don't add any)
but then actually don't break lightmap.h, so add one

accept everything iwyu suggests for these files

for all files that iwyu reports as (it should add or remove "input.h")
{
	add / remove "input.h" according to iwyu;
	remove everything iwyu reports to remove;
	while (doesn't compile) {add directly what needs to be added};
	/* note: thanks to indirect includes, we don't need to include most of what iwyu reports
	we obey iwyu only for "input.h", everything else is a suggestion if it doesn't compile without it */
}

split-off "input_context.h" and "input_enums.h" from "input.h" and "input_context.cpp" from "input.cpp"
"input_enums.h" contains things that both of the other header files need.
Therefor it is included in both of the header files.

…xcessive includes

for all files that iwyu reports as (it should add or remove "input.h" or "input_context.h")
{
        add / remove "input.h" and "input_context.h" according to iwyu;
        remove everything iwyu reports to remove;
        while (doesn't compile) {add directly what needs to be added};
        /* note: thanks to indirect includes, we don't need to include most of what iwyu reports
        we obey iwyu only for "input.h" and "input_context.h", everything else is a suggestion
        if it doesn't compile without it */
}