This is in preparation for wiring up debug info support for noncopyable
values. Originally this flag name made sense since it was set when we performed
consume operator checking. Now I am going to use it for noncopyable types as
well. I think the new name uses_moveable_value_debuginfo actually describes what
the flag is supposed to do, tell IRGen that the value may be moved since it
needs to use moveable value debug info emission.
This is just a quick fix to stop us from dropping live values such as m in the
following example:
```
public func addressOnlyVarTest<T : P>(_ x: T) {
var k = x
k.doSomething()
let m = _move(k)
m.doSomething()
k = x
k.doSomething()
}
```
Before this change, we would just drop m and one wouldn't even see it in the
debugger.
I am only doing this currently for cases where when we merge at least one
alloc_stack was moved. The reason why is that to implement this correctly, I
need to use llvm.dbg.addr and changing the debug info from using
llvm.dbg.declare -> llvm.dbg.addr requires statistics and needs to be done a
little later in the swift development process. If one of these alloc_stack had
the [moved] marker attached to it, we know the user /did/ use move so they have
in a sense opted into having a move function effect its program so we are only
changing how new code appears in the debugger.
