Fix problem where version script causes predefined hidden symbol to be defined twice.

Fix problem where version script causes predefined hidden symbol to be defined twice.

When creating a predefined hidden symbol like _GLOBAL_OFFSET_TABLE_, gold
was incorrectly letting a version script add a version to the symbol,
resulting in two copies of the symbol, both STB_LOCAL, but one of which
was grouped in the globals part of the symbol table.

gold/
	* symtab.cc (Symbol_table::define_special_symbol): Add is_forced_local
	parameter; if set, do not check version script.
	(Symbol_table::do_define_in_output_data): Pass is_forced_local for
	STB_LOCAL predefined symbols.
	(Symbol_table::do_define_in_output_segment): Likewise.
	(Symbol_table::do_define_in_output_segment): Likewise.
	(Symbol_table::do_define_as_constant): Likewise.
	* symtab.h (Symbol_table::define_special_symbol): Add is_forced_local
	parameter. Adjust all callers.
	* testsuite/Makefile.am (ver_test_8.sh): New test case.
	* testsuite/Makefile.in: Regenerate.
	* ver_test_8.sh: New test script.