LTO rescan archives

LTO rescan archives

ld ought to be more clever about where it puts LTO recompiled objects.
Ideally the recompiled objects ought to be ordered to the same place
their IR objects were, and files extracted from archives on the second
pass ought to go in the same place as they would if extracted on the
first pass.  This patch addresses the archive problem.  Without this
fix, objects extracted from archives might be placed after the crt
files intended to go at the end of an executable or shared library,
possibly causing exception handling failures.

	* ldlang.h (lang_input_statement_type): Expand comments.
	(LANG_FOR_EACH_INPUT_STATEMENT): Rewrite without casts.
	* ldlang.c (lang_for_each_input_file): Likewise.
	(load_symbols): Set usrdata for archives.
	(find_rescan_insertion): New function.
	(lang_process): Trim off and reinsert entries added to file chain
	when rescanning archives for LTO.
	* ldmain.c (add_archive_element): Set my_archive input_statement
	next pointer to last element added.