d: Use semanticRun to prevent declaration pass from running multiple times.

d: Use semanticRun to prevent declaration pass from running multiple times.

This shouldn't happen during normal traversal of the AST provided from
the front-end, however as there are some cases where declarations need
to be visited out of order, such as what is being done in PR d/89017, it
then becomes necessary to guard against this.

gcc/d/ChangeLog:

2019-04-21  Iain Buclaw  <ibuclaw@gdcproject.org>

	* decl.cc (DeclVisitor::visit(Import)): Set semanticRun after
	completion, guard against being called more than once.
	(DeclVisitor::visit(StructDeclaration)): Likewise.
	(DeclVisitor::visit(ClassDeclaration)): Likewise.
	(DeclVisitor::visit(InterfaceDeclaration)): Likewise.
	(DeclVisitor::visit(VarDeclaration)): Likewise.
	(DeclVisitor::visit(TypeInfoDeclaration)): Likewise.

From-SVN: r270478