Change LineNumber nodes to point at definition site

[Keno]

Before:

julia> @which rrule(typeof, 1.0)
rrule(::typeof(typeof), var"269"; kwargs...) in ChainRules at [...]/rule_definition_tools.jl:352

After:

julia> @which rrule(typeof, 1.0)
rrule(::typeof(typeof), var"269"; typeof_pullback) in ChainRules at [...]/src/rulesets/Core/core.jl:8

N.B.:, currently includes the commit from #308, because it touches the same code, but should be automatically rebased once that is in.

[oxinabox]

Yesss, thanks, i have been meeting to do this for ages.
Ever since #58
but working out how for multiexpression functions proved annoying.

It would be good to add this to the Julia docs?

[oxinabox]

Why is this a macro?

[Keno]

It operates on the quote itself, rather than the interpolated expression.

[oxinabox]

I see, can we add a comment to this effect? or a docstring?

[Keno]

Sure, feel free to add whatever you think would be helpful.

[oxinabox]

Is the following correct?

Suggested change

	macro strip_linenos(expr)
	"This should be put before a `quote`, to stop the quote from having line numbers recorded"
	macro strip_linenos(expr)

[Keno]

Well, that is how to use it, but it's a bit of an odd description of the macro. It just deleted linenumber nodes in whatever block you put it in front of. E.g. if you did:

@strip_linenos function foo(x)
<blah>
end

then that function wouldn't have line numbers either.

[oxinabox]

Needs rebasing and bumping the verison number then we can merge.

[oxinabox]

BlockDiagonals failure is unrelated.

[oxinabox]

ChainRules.jl failures are unrelated