subsumes request #454

dependencis -> dependencies

…uate arguments immediately.

Add the ability to evaluate some parts of a `@spawn`/`@async`
immediately, in the current thread context.

This prevents variables being "boxed" in order to capture them in the
closure, exactly the same as wrapping them in a let-block locally.

For example, `$x` expands like this:
```julia
julia> @macroexpand @async $x + 2
quote
    #= task.jl:361 =#
    let var"#JuliaLang#454" = x
        #= task.jl:362 =#
        local var"JuliaLang#9#task" = Base.Task((()->begin
                            #= task.jl:358 =#
                            var"#JuliaLang#454" + 2
                        end))
        #= task.jl:363 =#
        if $(Expr(:islocal, Symbol("##sync#95")))
            #= task.jl:364 =#
            Base.push!(var"##sync#95", var"JuliaLang#9#task")
        end
        #= task.jl:366 =#
        Base.schedule(var"JuliaLang#9#task")
        #= task.jl:367 =#
        var"JuliaLang#9#task"
    end
end
```

…immediately (#33119)

Adds $-interpolation syntax to `@async` and `Threads.@spawn`, to evaluate arguments immediately.

Add the ability to evaluate some parts of a `@spawn`/`@async`
immediately, in the current thread context.

This prevents variables being "boxed" in order to capture them in the
closure, exactly the same as wrapping them in a let-block locally.

For example, `$x` expands like this:
```julia
julia> @macroexpand @async $x + 2
quote
    #= task.jl:361 =#
    let var"##454" = x
        #= task.jl:362 =#
        local var"#9#task" = Base.Task((()->begin
                            #= task.jl:358 =#
                            var"##454" + 2
                        end))
        #= task.jl:363 =#
        if $(Expr(:islocal, Symbol("##sync#95")))
            #= task.jl:364 =#
            Base.push!(var"##sync#95", var"#9#task")
        end
        #= task.jl:366 =#
        Base.schedule(var"#9#task")
        #= task.jl:367 =#
        var"#9#task"
    end
end
```

…immediately (#33119)

Adds $-interpolation syntax to `@async` and `Threads.@spawn`, to evaluate arguments immediately.

Add the ability to evaluate some parts of a `@spawn`/`@async`
immediately, in the current thread context.

This prevents variables being "boxed" in order to capture them in the
closure, exactly the same as wrapping them in a let-block locally.

For example, `$x` expands like this:
```julia
julia> @macroexpand @async $x + 2
quote
    #= task.jl:361 =#
    let var"##454" = x
        #= task.jl:362 =#
        local var"#9#task" = Base.Task((()->begin
                            #= task.jl:358 =#
                            var"##454" + 2
                        end))
        #= task.jl:363 =#
        if $(Expr(:islocal, Symbol("##sync#95")))
            #= task.jl:364 =#
            Base.push!(var"##sync#95", var"#9#task")
        end
        #= task.jl:366 =#
        Base.schedule(var"#9#task")
        #= task.jl:367 =#
        var"#9#task"
    end
end
```

More info: exercism/org-wide-files@d31ac9e

This supports SSAValue args for cglobal while also fixing a bug
in which a GotoIfNot ended up going to the wrong statement.
The latter was a consequence of incorrect :call unnesting.

Fixes #455
Fixes #454
Fixes #415
Fixes JuliaDebug/Debugger.jl#275
Improves #354