Fix problem where __start_ and __stop_ section symbols do not honor version script.

Fix problem where __start_ and __stop_ section symbols do not honor version script.

When creating the special __start_ and __stop_ section symbols, gold
does not check the version script to see if they should be local
instead of global.

2015-07-21  Cary Coutant  <ccoutant@gmail.com>

gold/
	PR gold/18548
	* symtab.cc (Symbol_table::do_define_in_output_data): Check for
	forced local symbol even when oldsym != NULL.
	(Symbol_table::do_define_in_output_segment): Likewise.
	(Symbol_table::do_define_as_constant): Likewise.