Copy-paste error in trunnel.md
In https://gitweb.torproject.org/trunnel.git/blob/599017a1bf98fe824691509ee6df9f4922460054:/doc/trunnel.md#l161:
```
u8 value_a;
u16 value_b;
u32 value_c;
u32 value_d;
```
Last line should have `u64`.
issue