[Sema] Make extended vectors of `bool` an error.
In OpenCL, `bool` vectors are a reserved type, and are therefore
illegal.
Outside of OpenCL, if we try to make an extended vector of N `bool`s,
Clang will lower it to an `[N x i1]`. LLVM has no ABI for bitvectors, so
lots of operations on such vectors are thoroughly broken. As a result,
this patch makes them illegal in everything else, as well. :)
Differential Revision: http://reviews.llvm.org/D15721
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@259011
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