Fix module export symbols should not be marked as having non-local references

[boingoing]

When we do BindPidRefsInScope, we walk the PidRef stack and check to see
if any ref is non-local. Global and module export symbols should never be
marked as non-local.

Problem is that not all refs in the PidRef stack are necessarily marked to
indicate that the symbol is a module export. If a symbol which is an
export has a non-local ref which does not indicate it is a module export,
we will erroneously set the hasNonLocalReference flag on that symbol.

Here's an example of how this can happen:
function foo() { };
export { foo };

In this case, the top ref to symbol foo does not say that foo is a module
export so we might set the hasNonLocalReference flag on symbol foo when we
look at the top ref. The next ref in the PidRef stack would indicate that
foo is a symbol but by then we've already marked it.

A fix is to move the module export flag out of PidRef and into the Ident
itself. Then we can check to see if the pid is a module export before we
walk the PidRef stack in BindPidRefsInScope.

[boingoing]

@pleath this is the restructuring of the PidRef module export flag we talked about. Could you give it a glance?

[pleath]

Cool. Nice that this could be resolved with a simple change.

[pleath]

👍

[boingoing]

@dotnet-bot please test windows x64_release

[boingoing]

@dotnet-bot please test OSX osx_osx_debug_static