[AVX512] Added VPCMPEQ intrinisics to headers.
Added tests.

Patch by Maxim Blumenthal <maxim.blumenthal@intel.com>


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@219319 91177308-0d34-0410-b5e6-96231b3b80d8