swift234

Replace ExprStmtOrDecl with ASTNode and make it a struct.

Previously, the Parser and BranchStmt typedef-ed ExprStmtOrDecl as a pointer union. Using typedef made the objects compatible, but did not allow us to extend the type with helper methods, such as getSourceRange(), which is something you can get on all of the AST objects. This patch introduces ASTNode that subclasses from PointerUnion and is used by both parser and BranchStmt.

Swift SVN r9971