[cleanup] Removed unused struct stack from IRState.
Fixed getParentFunc(..., true) as used for nested context creation.

It seems like the original code contained two issues: First,
the stopOnStatic branch checked the passed symbol over and
over again instead of the current parent. Second, aggregate
declarations are not Declarations, they are ScopeDsymbols.

GitHub: Fixes #696.
Merge pull request #738 from klickverbot/nested-static

Fixed getParentFunc(..., true) as used for nested context creation.