pbc_dump: don't skip varargs words in -d mode

[Austin_Hastings]

See #1425 for an example of this, but when pbc_dump is running in -d mode (disassemble opcodes), it silently skips over varargs parameters to the various call support ops. An example:

 0070:  00000023 00000022                                     set_args_pc
 0076:  00000024 0000000f                                     get_results_pc

But the pbc contains:

 0070:  00000023 00000022 00000001 0000001e 00000020 00000026 00000024 0000000f 

The varargs parameters (001, 01e, 020, 026) were silently omitted from the output in -d mode. The best possible scenario would be to decode the op sufficiently to identify the meanings of the parameters -- this is P0, that is Constant-123, that is a string, etc. But even just including the data in-line would be helpful:

 0070:  00000023 00000022                                     set_args_pc
     :      00000001 0000001e                                   -- varargs data
     :      00000020 00000026                                   -- varargs data
 0076:  00000024 0000000f                                     get_results_pc