AVX-512: Scalar ERI intrinsics

including SAE mode and memory operand.
Added AVX512_maskable_scalar template, that should cover all scalar instructions in the future.

The main difference between AVX512_maskable_scalar<> and AVX512_maskable<> is using X86select instead of vselect.
I need it, because I can't create vselect node for MVT::i1 mask for scalar instruction.

http://reviews.llvm.org/D6378

llvm-svn: 222820