A few follow-up fixes for GUC name quoting

Fixups for 17974ec259: Some messages were missed (and some were new
since the patch was originally proposed), and there was a typo
introduced.

src/backend/postmaster/pgarch.c

@@ -895,7 +895,7 @@ HandlePgArchInterrupts(void)
 			 */
 			ereport(LOG,
 					(errmsg("restarting archiver process because value of "
-							"archive_library was changed")));
+							"\"archive_library\" was changed")));
 
 			proc_exit(0);
 		}