Improve support for type-generic vector intrinsics by teaching TableGen how

Improve support for type-generic vector intrinsics by teaching TableGen how
to handle LLVMMatchType intrinsic parameters, and by adding new subclasses
of LLVMMatchType to match vector types with integral elements that are
either twice as wide or half as wide as the elements of the matched type.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61834 91177308-0d34-0410-b5e6-96231b3b80d8