Remove x86_sse42_crc32_64_8 intrinsic. It has no functional difference from x86_sse42_crc32_32_8 and was not mapped to a clang builtin. I'm not even sure why this form of the instruction is even called out explicitly in the docs. Also add AutoUpgrade support to convert it into the other intrinsic with appropriate trunc and zext.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192672 91177308-0d34-0410-b5e6-96231b3b80d8