separate shrink-wrap: New command-line flag, status flag, hooks, and doc

separate shrink-wrap: New command-line flag, status flag, hooks, and doc

This patch adds a new command-line flag "-fshrink-wrap-separate", a status
flag "shrink_wrapped_separate", hooks for abstracting the target components,
and documentation for all those.

	* common.opt (-fshrink-wrap-separate): New flag.
	* doc/invoke.texi: Document it.
	* doc/tm.texi.in (Shrink-wrapping separate components): New subsection.
	* doc/tm.texi: Regenerate.
	* emit-rtl.h (struct rtl_data): New field shrink_wrapped_separate.
	* target.def (shrink_wrap): New hook vector.
	(get_separate_components, components_for_bb, disqualify_components,
	emit_prologue_components, emit_epilogue_components,
	set_handled_components): New hooks.

From-SVN: r241059