This patch fixes the printer for the `llvm.switch` operation with
negative values in a case.
The previous behaviour printed the value as an unsigned integer, as the
`getLimitedValue()` returns unsigned value. This caused the roundtrip to
fail (assertion in `APInt`), as the printed unsigned integer could not
be parsed into the same amount of bits in a signed integer.
I don't see a good reason for keeping any restriction on the printed
value, as LLVMIR `switch` afaik does not have a limit on the bitwidth of
the values and `APInt` handles printing just fine.
59f407020e