stage2: un-tangle memory management of Decl and Namespace

Before there was this "top_decl" and "tmp_namespace" stack values that
were kludgy and buggy. Now Sema is slightly reworked so that files which
are structs are analyzed with their own Decl and Namespace already set
up.

After this commit there are no memory leaks for a successful build-obj.
2d8d681b5eAndrew Kelley committed on 4/30/2021, 6:07:31 PMparent5d696b0
3 files changedLine totals unavailable