Apply TLC to vect_analyze_early_break_dependences

Apply TLC to vect_analyze_early_break_dependences

There has been some confusion in my understanding of how early breaks
work, the following clarifies some comments and undoes one change that
shouldn't have been necessary.  It also fixes the dependence test
to avoit TBAA (we're moving stores down across loads).

	* tree-vect-data-refs.cc (vect_analyze_early_break_dependences):
	Only check whether reads are in-bound in places that are not safe.
	Fix dependence check.  Add missing newline.  Clarify comments.