Implement C++11 delegating constructors.

Implement C++11 delegating constructors.

	* cp-tree.h (enum cpp0x_warn_str): Add CPP0X_DELEGATING_CTORS.
	* error.c (maybe_warn_cpp0x): Adjust.
	* parser.c (cp_parser_mem_initializer_list): Use it.  Diagnose
	multiple initializers if a delegating initializer is present.
	* call.c (build_special_member_call): Convert an assert into an if.
	* init.c (perform_target_ctor): New.
	(emit_mem_initializers): Use it.
	(expand_member_init, expand_default_init): Adjust.

Co-Authored-By: Pedro Lamarão <pedro.lamarao@gmail.com>
From-SVN: r182012