Allow bitcasting of fp/vec values into inline assembly 'r' operands, int/vec operands into 'f' operands, and int/fp operands into 'v' operands. This now matches GCCs behavior.
For the 'f' constraint, I changed the register class assigned for 128-bit to depend on the vector facility (using getRegClassFor()). This was needed to match GCCs behavior, but I am now a little surprised that this was always FP128BitRegClass..?
The casting between i128 and f128 required some extra work as i128 is untyped.
All this CW_Default stuff is confusing - isn't this, well, the default?