[.data.table fails with complex/raw columns

[richierocks]

To reproduce, try:

DT <- data.table(x = as.complex(1:5))
DT[1]
## Error in `[.data.table`(DT, 1) : Unknown column type 'complex'

Similarly:

DT <- data.table(x = as.raw(1:5))
DT[1]
## Error in `[.data.table`(DT, 1) : Unknown column type 'raw'

The problem appears to be originating from the line:

ans[[target]] = .Call(CsubsetVector,x[[source]],irows)

Loosely related issue: #602