"proot-of-work" to "proof-of-work"

trie: fix a temporary memory leak in the memcache

* p2p/discover: move bond logic from table to transport

This commit moves node endpoint verification (bonding) from the table to
the UDP transport implementation. Previously, adding a node to the table
entailed pinging the node if needed. With this change, the ping-back
logic is embedded in the packet handler at a lower level.

It is easy to verify that the basic protocol is unchanged: we still
require a valid pong reply from the node before findnode is accepted.

The node database tracked the time of last ping sent to the node and
time of last valid pong received from the node. Node endpoints are
considered verified when a valid pong is received and the time of last
pong was called 'bond time'. The time of last ping sent was unused. In
this commit, the last ping database entry is repurposed to mean last
ping _received_. This entry is now used to track whether the node needs
to be pinged back.

The other big change is how nodes are added to the table. We used to add
nodes in Table.bond, which ran when a remote node pinged us or when we
encountered the node in a neighbors reply. The transport now adds to the
table directly after the endpoint is verified through ping. To ensure
that the Table can't be filled just by pinging the node repeatedly, we
retain the isInitDone check. During init, only nodes from neighbors
replies are added.

* p2p/discover: reduce findnode failure counter on success

* p2p/discover: remove unused parameter of loadSeedNodes

* p2p/discover: improve ping-back check and comments

* p2p/discover: add neighbors reply nodes always, not just during init

* core/vm: A pool for int pools

* core/vm: fix rebase issue

* core/vm: push leftover stack items after execution, not before

* cmd/geth: add flags for metrics export

* cmd/geth: update usage fields for metrics flags

* metrics/influxdb: update reporter logger to adhere to geth logging convention

remove formatting from ResettingTimer metrics if requested in raw format

spell correction from `repors` to `reports`

build: make build/goimports.sh more potable

* core/vm: clear linter warnings

* core/vm: review input

* core/vm.go: revert lint in noop as per request

log: Change time format

- Keep the tailing zeros.
- Limit precision to milliseconds.

* les: handle conn/disc/reg logic in the eventloop

* les: try to dial before start eventloop

* les: handle disconnect logic more safely

* les: grammar fix

Swarm POC3 - happy solstice

The current trie memory database/cache that we do pruning on stores
trie nodes as binary rlp encoded blobs, and also stores the node
relationships/references for GC purposes. However, most of the trie
nodes (everything apart from a value node) is in essence just a
collection of references.

This PR switches out the RLP encoded trie blobs with the
collapsed-but-not-serialized trie nodes. This permits most of the
references to be recovered from within the node data structure,
avoiding the need to track them a second time (expensive memory wise).

remove the tail "," from genesis config,  which will cause genesis config parse error .

eth/tracers: fix err in 4byte, add some opcode analysis tools

* core: move test util var/func to test file

* core: remove useless func

* cmd/faucet: authGitHub is not used anymore

* cmd/puppeth: remove not used code

* debug: Use pprof goroutine writer in debug.Stacks() to ensure all goroutines are captured.

* Up to 64MB limit, previous code only captured first 1MB of goroutines.

* internal/debug: simplify stacks handler

* fix typo

* fix pointer receiver