* i386.cc (class Output_data_plt_i386): Add layout_ field.

	* i386.cc (class Output_data_plt_i386): Add layout_ field.
	(Output_data_plt_i386::Output_data_plt_i386): Initialize layout_.
	(Output_data_plt_i386::do_write): Write address of .dynamic
	section to first entry in .got.plt section.
	* x86_64.cc (class Output_data_plt_x86_64): Add layout_ field.
	(Output_data_plt_x86_64::Output_data_plt_x86_64) [both versions]:
	Initialize layout_.
	(Output_data_plt_x86_64::do_write): Write address of .dynamic
	section to first entry in .got.plt section.
	* layout.h (Layout::dynamic_section): New function.