core: chain fork fix

Makefile improvements

Chain reorgs weren't properly handled when a chain was further ahead.
Previously we'd end up with mixed chains in our canonical numbering
sequence. Added test for this type of forking.

```
     /-o-o-o   A
o-C-+
     \-o-o-o-o B
```

Ends up with with C A1, A2, A3, B4

Insert blocks will no longer allow processing of multiple chains at the
same time. The block lock has been moved to start of the function.

Remove path separator literals

The default value of the Shh option is true, but cli can't
see it because it is not part of the mist options.

This is necessary because cli doesn't see the default
value unless the flag is included.

This ensures that compiler error messages contain the correct path.

p2p/discover: fix api issues caused by leveldb update

rlp: fix list bounds check overflow (found by go-fuzz)

p2p/discover: persistent node database

godeps: refresh leveldb, clean up stale dependencies

Conflicts:
	rpc/api.go

Whisper cleanup, part 3

The list size checking overflowed if the size information
for a value was bigger than the list. This is resolved by
always performing the check before reading.