Don't use INSERT_SUBREG to model anyext operations on x86-64, as it

Don't use INSERT_SUBREG to model anyext operations on x86-64, as it
leads to partial-register definitions. To help avoid redundant
zero-extensions, also teach the h-register matching patterns that
use movzbl to match anyext as well as zext.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80099 91177308-0d34-0410-b5e6-96231b3b80d8