[PATCH] Using Masked Load / Store intrinsics in Loop Vectorizer

[Elena Demikhovsky]

To Michael: 
Some tests fail in this case, I tried. Because NumberOfStoresToPredicate allows you to predicated some stores without masking.
I wanted to keep this knob as is.
I also do not check mayThrow() because it is for calls only.

To Nadav:
> Maybe a better name would be "isMaskRequired"?
No problem

http://reviews.llvm.org/D6527