arc devel

[Araq]

more ARC related bugfixes and refactorings

[Araq]

@cooldome please test this branch with your codebase.

[cooldome]

Sure, can do it on Monday

[cooldome]

I wanted to try this one today but I have found that thanks to the #12766 fix, the code now compiles
with latest Nim devel but I get crashes at the runtime. Need to chase them down.
One was very weird, when I compile the whole project a simple proc in one module:

proc add(c: Container, x: sink MyValue)

didn't get the destructor injection for x argument. But when I compile just this module it gets destructor injection. No generics, no inline.

Will keep on debugging and compare generated code.

[Araq]

@cooldome If the current devel cannot compile your projects we might as well go ahead and merge this PR, right?

[cooldome]

Yes, looks like is going to take some time to trace it down. Please submit and we can fix it later.

[narimiran]

Note to the person who will merge this: beware that some of the commits have [backport] tag. Merge carefully :)

EDIT: I've just been told that those two commits are already in devel. I'm squashing+merging this then.