lcm.c: Move all mode-switching related functions from here...

	* lcm.c: Move all mode-switching related functions from here...
	* mode-switching.c: ...to this new file.
	* doc/passes.texi: Update accordingly.

	* basic-block.h (label_value_list): Remove extern decl.
	* cfgrtl.c (label_value_list): Remove.
	(can_delete_label_p): Don't look at it.
	* cfgcleanup.c (cleanup_cfg): Don't free it.

	* common.opt: Don't refer to non-existing flag_alias_check.

From-SVN: r100591