This fixes the lldb disassembler script so that it doesn't need a live
process when disassembling rb_iseq_t.  I also added the PC to the output
so you can tell what the VM is executing when it crashed.

For example:

```
(lldb) rbdisasm ec->cfp->iseq
PC             IDX  insn_name(operands)
0x56039f0a1720 0000 nop
0x56039f0a1728 0001 getlocal_WC_1( 5 )
0x56039f0a1738 0003 branchunless( 7 )
0x56039f0a1748 0005 getlocal_WC_0( 3 )
0x56039f0a1758 0007 putstring( (VALUE)0x56039f0c7eb8 )
0x56039f0a1768 0009 opt_send_without_block( (struct rb_call_data *)0x56039f09f140 )
0x56039f0a1778 0011 pop
0x56039f0a1780 0012 getglobal( ID: 0x7fd7 )
0x56039f0a1790 0014 branchunless( 7 )
0x56039f0a17a0 0016 getlocal_WC_0( 3 )
0x56039f0a17b0 0018 putstring( (VALUE)0x56039f0c7e90 )
0x56039f0a17c0 0020 opt_send_without_block( (struct rb_call_data *)0x56039f09f150 )
0x56039f0a17d0 0022 pop
0x56039f0a17d8 0023 getlocal_WC_0( 3 )
0x56039f0a17e8 0025 putobject( (VALUE)0x56039f0c7e68 )
0x56039f0a17f8 0027 getlocal_WC_1( 6 )
0x56039f0a1808 0029 dup
0x56039f0a1810 0030 checktype( 5 )
0x56039f0a1820 0032 branchif( 4 )
0x56039f0a1830 0034 dup
0x56039f0a1838 0035 opt_send_without_block( (struct rb_call_data *)0x56039f09f160 )
0x56039f0a1848 0037 tostring
0x56039f0a1850 0038 putobject( (VALUE)0x56039f0c7e40 )
0x56039f0a1860 0040 concatstrings( 3 )
0x56039f0a1870 0042 opt_send_without_block( (struct rb_call_data *)0x56039f09f170 )
0x56039f0a1880 0044 nop
0x56039f0a1888 0045 leave
(lldb) p ec->cfp->pc
(const VALUE *) $146 = 0x000056039f0a1848
```

Here we can see the VM is currently executing `opt_send_without_block`
(because the PC is one ahead of the current instruction)