Fix compile errors with GCC 4.2.

Fix compile errors with GCC 4.2.

gold/
	PR gold/21040
	* x86_64.cc (Output_data_plt_x86_64_bnd::do_fill_first_plt_entry):
	Remove unnecessary 'typename' keyword.
	(Output_data_plt_x86_64_bnd::do_fill_plt_entry): Likewise.
	(Output_data_plt_x86_64_bnd::do_fill_tlsdesc_entry): Likewise.
	(Output_data_plt_x86_64_bnd::fill_aplt_entry): Likewise.
	* testsuite/copy_test_relro_1.cc (p, b, c, q): Add separate extern
	declarations.