Previously I packed standard library variable arguments as well as
file operation into one define `NK_INCLUDE_STANDARD_IO`. This caused
some problems and I split the define into two. So if you want the old
behavior you need to define `NK_INCLUDE_STANDARD_IO` as well as
`NK_INCLUDE_STANDARD_VARARGS`. If you only want file operations but
not variable arguments only define `NK_INCLUDE_STANDARD_IO` and
if you only want varargs but not file operations please only define
`NK_INCLUDE_STANDARD_VARARGS`.
