Added Skylake client to X86 targets and features

Changes in X86.td:

I set features of Intel processors in incremental form: IVB = SNB + X HSW = IVB + X ..
I added Skylake client processor and defined it's features
FeatureADX was missing on KNL
Added some new features to appropriate processors SMAP, IFMA, PREFETCHWT1, VMFUNC and others

Differential Revision: http://reviews.llvm.org/D16357

llvm-svn: 258659