Support noexcept-specifications for transaction statements and expressions.

Support noexcept-specifications for transaction statements and expressions.

	gcc/cp/
	* semantics.c (finish_transaction_stmt, build_transaction_expr):
	Accept new noexcept parameter and handle it.
	* cp-tree.h (finish_transaction_stmt, build_transaction_expr): Adapt
	declarations.
	* parser.c (cp_parser_exception_specification_opt): Extract
	noexcept-specification parsing to ...
	(cp_parser_noexcept_specification_opt): ...here.  Allow for parsing
	non-constexpr noexcept arguments.
	(cp_parser_transaction, cp_parser_transaction_expression): Parse
	and handle noexcept-specifications.
	(cp_parser_function_transaction): Adapt to finish_transaction_stmt
	change.
	* pt.c (tsubst_expr): Adapt to new noexcept parameters when
	building transactions.

	gcc/testsuite/
	* g++.dg/tm/noexcept-1.C: New test.
	* g++.dg/tm/noexcept-2.C: New test.
	* g++.dg/tm/noexcept-3.C: New test.
	* g++.dg/tm/noexcept-4.C: New test.
	* g++.dg/tm/noexcept-5.C: New test.

From-SVN: r182234