Catch invalid bitwise operation on vector of floats

Bitwise complement applied to vector of floats described with
attribute `ext_vector_type` is not diagnosed as error. Attempt to
compile such construct causes assertion violation in Instruction.cpp.
With this change the complement is treated similar to the case of
vector type described with attribute `vector_size`.

Differential Revision: https://reviews.llvm.org/D33732

llvm-svn: 304963