Get actual function in meta.context

[Mte90]

So discussing with @hdwalters on #586 we saw a flaw.
My solution is hacky and does't work with all the cases because I am just counting where it should be the function but in some cases could be different as exposed.

So ideally there should be on meta.context instead of just the token what is the function (and the line) that is actually parsing so we can have better information.
I think that can be useful also in other cases but until we don't have yet we can't provide insightful errors in the compiler.