1) extend loop-peeling to support loop nests.
  2) with alignment analysis turned off, vectorizer now can do
     outer-loop vectorization with the loop trip count not evenly
     divided by VF and generate two vectorized loop with two different
     vector sizes.
  3) TODO: extend alignment analysis to work with loop peeling on loop nests.

	modified:   gcc/cfgloop.h
	modified:   gcc/common.opt
	modified:   gcc/tree-vect-loop-manip.c
	modified:   gcc/tree-vect-loop.c
	modified:   gcc/tree-vectorizer.c
	modified:   gcc/tree-vectorizer.h