Revert the vector part of Enrico's change in r198729;

it is causing an llvm assert when run against
test/functionalities/data-formatter/rdar-10642615,

Assertion failed: (isa<X>(Val) && "cast<Ty>() argument of incompatible type!"), function cast, file llvm/include/llvm/Support/Casting.h, line 239.

llvm-svn: 198809