DIP 1029---Add throw as Function Attribute---Community Review Round 1

[Adam D. Ruppe]

On Tuesday, 14 January 2020 at 22:30:40 UTC, Walter Bright wrote:
> Hence, when "nothrow" becomes the default

IF, not when. I support this DIP as a nice independent move, but 
I am going to fight you on the step of changing the default.

But, my plan here:
http://dpldocs.info/this-week-in-d/Blog.Posted_2020_01_13.html#my-attribute-proposal---no-changes-to-defaults

to make `nothrow:` (etc) go into the child scopes except 
templates means we have a less disruptive way to make this work 
without formally changing the defaults.