* ldlang.h (lang_output_section_statement_type): Add update_dot_tree.

	* ldlang.h (lang_output_section_statement_type): Add update_dot_tree.
	(lang_enter_overlay): Remove the last two parameters.
	(lang_leave_overlay): Take them here instead.
	* ldgram.y (memspec_at_opt): Set $$ to null if no region is given.
	(section): Pass LMA and crossref flag to lang_leave_overlay rather
	than lang_enter_overlay.
	* ldlang.c (lang_memory_region_lookup): Return null for null names.
	(lang_output_section_statement_lookup): Initialize update_dot_tree.
	(lang_size_sections_1): Evaluate it.
	(lang_leave_output_section_statement): Rework LMA lookup.
	(overlay_lma, overlay_nocrossrefs): Remove.
	(lang_enter_overlay): Remove LMA and corssref arguments.
	(lang_enter_overlay_section): Don't set the LMA here.
	(lang_leave_overlay): Take LMA and crossref arguments.  Move the '.'
	assignment to the last section's update_dot_tree.  Unconditionally
	use the load and run-time regions specified in the OVERLAY statement.
	Likewise the first section's LMA.  Only set the other sections' LMAs
	when no load region is given.