hex_to_pod needs the destination as an arg, as opposed to it returning the pod
added double-check for 202612 block id

if a new block has the same block id as 202612 but the wrong blobdata,
this will tell the caller that the block id is actually null_hash rather
than the 202612 block id.
override for get_block_longhash for block 202612
Fix tree-hash cnt n^2. Asserts, comment. Squash2
checkpoints on restore; currently fails on 212 checkpoint
bug fix to checkpoint-on-restore; still fails on 612
fix checkpoints
Merge pull request #121 from fluffypony/master

Fix tree_hash, patch for bad block 202612