* Remove deprecated PanicXXX functions from codebase

As per discussion over
[here](https://github.com/tendermint/tendermint/pull/3456#discussion_r278423492),
we need to remove these `PanicXXX` functions and eliminate our
dependence on them. In this PR, each and every `PanicXXX` function call
is replaced with a simple `panic` call.

* add a changelog entry

* p2p: refactor Switch#Broadcast func

- call wg.Add only once
- do not call peers.List twice!
  * bad for perfomance
  * peers list can change in between calls!

Refs #3306

* p2p: use time.Ticker instead of RepeatTimer

no need in RepeatTimer since we don't Reset them

Refs #3306

* libs/common: remove RepeatTimer (also TimerMaker and Ticker interface)

"ancient code that’s caused no end of trouble" Ethan

I believe there's much simplier way to write a ticker than can be reset
https://medium.com/@arpith/resetting-a-ticker-in-go-63858a2c17ec

* p2p/conn: fix deadlock in FlushStop/OnStop

* makefile: set_with_deadlock

* close doneSendRoutine at end of sendRoutine

* conn: initialize channs in OnStart

* p2p/pex: failing test

* p2p/conn: add stopMtx for FlushStop and OnStop

* changelog

Fixes #2715

In crawlPeersRoutine, which is performed when seedMode is run, there is
logic that disconnects the peer's state information at 3-hour intervals
through the duration value. The duration value is calculated by
referring to the created value of MConnection. When MConnection is
created for the first time, the created value is not initiated, so it is
not disconnected every 3 hours but every time it is disconnected. So,
normal nodes are connected to seedNode and disconnected immediately, so
address exchange does not work properly.

https://github.com/tendermint/tendermint/blob/master/p2p/pex/pex_reactor.go#L629
This point is not work correctly.
I think,
https://github.com/tendermint/tendermint/blob/master/p2p/conn/connection.go#L148
created variable is missing the current time setting.

* p2p/conn: FlushStop. Use in pex. Closes #2092

In seed mode, we call StopPeer immediately after Send.
Since flushing msgs to the peer happens in the background,
the peer connection is often closed before the messages are
actually sent out. The new FlushStop method allows all msgs
to first be written and flushed out on the conn before it is closed.

* fix dummy peer

* typo

* fixes from review

* more comments

* ensure pex doesn't call FlushStop more than once

FlushStop is not safe to call more than once,
but we call it from Receive in a go-routine so Receive
doesn't block.

To ensure we only call it once, we use the lastReceivedRequests
map - if an entry already exists, then FlushStop should already have
been called and we can return.

* catch up with amino changes in
https://github.com/tendermint/go-amino/pull/222

* WIP: update to amino v0.13.0

* update to fixed amino release

* Disable transitioning to new round upon 2/3+ of Precommit nils

Pull in ensureVote test function from https://github.com/tendermint/tendermint/pull/2132

* Add several ensureX test methods to wrap channel read with timeout

* Revert panic in tests

* Add additional metrics to p2p and consensus
Partially addresses https://github.com/cosmos/cosmos-sdk/issues/2169.
* WIP
* Updates from code review
* Updates from code review
* Add instrumentation namespace to configuration
* Fix test failure
* Updates from code review
* Add quotes
* Add atomic load
* Use storeint64
* Use addInt64 in writePacketMsgTo

* libs: Remove usage of custom Fmt, in favor of fmt.Sprintf

Closes #2193

* Fix bug that was masked by custom Fmt!

This reverts commit d02c5d1e30.

except now we calculate the max size using the maxPacketMsgSize()
function, which frees developers from having to know amino encoding
details.

plus, 10 additional bytes are added to leave the room for amino upgrades
(both making it more efficient / less efficient)

Fixes #1762#issuecomment-398940107

This reverts commit 96a3502

Fixes https://github.com/cosmos/cosmos-sdk/issues/1045

As both configs are concerned with the p2p packaage and PeerConfig is
only used inside of the package there is no good reason to keep the
couple of fields separate, therefore it is collapsed into the more
general P2PConifg. This is a stepping stone towards a setup where the
components inside of p2p do not have any knowledge about the config.

follow-up to #1325

Closes #1227

* use increment and decrement operators.

* remove unnecessary else branches.

* fix package comment with leading space.

* fix receiver names.

* fix error strings.

* remove omittable code.

* remove redundant return statement.

* Revert changes (code is generated.)

* use cfg as receiver name for all config-related types.

* use lsi as the receiver name for the LastSignedInfo type.

Refs #1205

* extract stopPongTimer method
* TestMConnectionMultiplePings

don't bother with this "only ping when we havent heard from them". lets
just always ping every peer from the sendRoutine every 10s no matter
what. if they dont pong within pongTimeout, disconnect :)