These two functions just call push_function_context_to and
pop_function_context_from, whose arguments are unused. Therefore, this
patch just leaves the zero-argument variants and remove the one-argument
functions.
Also, the langhooks are used only by the C front-end. After the
simplification that goes on in function.c, and given that the C
front-end only calls the function when it knows that cfun != 0, I think
it's better to provide wrappers for {push,pop}_function_context instead,
and call those from the front-end.
This is what the patch (bootstrapped/regtested i686-pc-linux-gnu) does.
Ok for mainline?