searchrawtransactions: fix vinextra arg clobbering any following args

[chappjc]

A nil pointer value signals that nothing was input for the argument and any following arguments must be defaults. So if you want to set reverse=true and vinextra=false, you cannot do it.

[chappjc]

To be more explicit:

includePrevOut, reverse := false, true
SearchRawTransactionsVerbose(address, 0, count, includePrevOut, reverse, nil)

Won't reverse because of includePrevOut being false and setting SearchRawTransactionsCmd.VinExtra to a nil pointer instead of a pointer to an int that equals 0.