* var-tracking.c (vars_copy_1): Cleanup and speedup chain operations.

	(vars_copy): Likewise.
	(variable_union): Likewise.
	(set_variable_part): Likewise.
	(delete_variable_part): Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@79304 138bc75d-0d04-0410-961f-82ee72b054a4