Change Type::isFloatingType() to reflect the actual definition of a

Change Type::isFloatingType() to reflect the actual definition of a
"floating type" in C, which does not include vector types. Introduce
Type::hasFloatingRepresentation() for the places where we want to know
whether the underlying representation is one or more floating-point
values. Remove some hacks we had where the former behavior of
Type::isFloatingType() was at odds with the language definition of the
term.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@106584 91177308-0d34-0410-b5e6-96231b3b80d8