swift

94445346 - AST: Handle MacroExpansionDecl in DeclExportabilityVisitor.

AST: Handle MacroExpansionDecl in DeclExportabilityVisitor. Instances of `MacroExpansionDecl` may be found in the AST when declarations are expanded from freestanding declaration macros and therefore exportability computations must be prepared to handle them. Resolves rdar://119449439