* lint: golint issue fixes

- on my local machine golint is a lot stricter than the bot so slowly going through and fixing things.

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* more fixes from golint

* remove isPeerPersistentFn

* add changelog entry

* libs/common: Refactor libs/common 5

- move mathematical functions and types out of `libs/common` to math pkg
- move net functions out of `libs/common` to net pkg
- move string functions out of `libs/common` to strings pkg
- move async functions out of `libs/common` to async pkg
- move bit functions out of `libs/common` to bits pkg
- move cmap functions out of `libs/common` to cmap pkg
- move os functions out of `libs/common` to os pkg

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* fix testing issues

* fix tests

closes #41417

woooooooooooooooooo kill the cmn pkg

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add changelog entry

* fix goimport issues

* run gofmt

* libs/common: refactor libs/common 2

- move random function to there own pkg

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* change imports and usage throughout repo

* fix goimports

* add changelog entry

Refs #3262

* make govet linter pass

Refs #3262

* close PipeReader and check for err

* Fix random distribution in bitArray.PickRandom

Previously it was very biased. 63 "_" followed by a single "x" had
much greater odds of being chosen. Additionally, the last element was
skewed. This fixes that by first preproccessing the set of all true
indices, and then randomly selecting a single element from there.

This commit also makes the code here significantly simpler, and
improves test cases.

* unlock mtx right after we select true indices

also, fix potential bug in Or function

This now makes bit array functions which take in a second bit array, thread
safe. Previously there was a warning on bitarray.Update to be lock the
second parameter externally if thread safety wasrequired.
This was not done within the codebase, so it was fine to change here.

Closes #2080

This reverts commit d02c5d1e30.

See CHANGELOG

* use increment and decrement operators.

* remove unnecessary else branches.

* fix receiver names.

* remove omittable code.

* fix dot imports.

Fixes #169
Fixes https://github.com/tendermint/tendermint/issues/1322

The previous code was very trusting assuming that
rational actors will use this code. However, Byzantine
actors don't care and in the case of the linked issue
negative lengths can be sent to this code unfettered
having been received from a peer.

This code is essentially just a sign change from
`==`
to
`<=`

and we've gutted out that attack by being more defensive.

Fixes #169
Fixes https://github.com/tendermint/tendermint/issues/1322

The previous code was very trusting assuming that
rational actors will use this code. However, Byzantine
actors don't care and in the case of the linked issue
negative lengths can be sent to this code unfettered
having been received from a peer.

This code is essentially just a sign change from
`==`
to
`<=`

and we've gutted out that attack by being more defensive.

Fixes https://github.com/tendermint/tmlibs/issues/145
Fixes https://github.com/tendermint/tmlibs/issues/146

The code in here has been fragile when it comes to nil
but these edge cases were never tested, although they've
showed up in the wild and were only noticed because
the reporter actually read the logs otherwise
we'd have never known.

This changes covers some of these cases and adds some tests.

Update previously only checked that the receiver was
non-nil but didn't check that the input parameter to update
"o" was non-nil causing a nil dereference in cases such as
fe632ea32a/consensus/reactor.go (L306)

Fixes https://github.com/tendermint/tendermint/issues/1169

Fixes https://github.com/tendermint/tmlibs/issues/99
Updates https://github.com/tendermint/tendermint/issues/973

Removed usages of math/rand.DefaultSource in favour of our
own source that's seeded with a completely random source
and is safe for use in concurrent in multiple goroutines.
Also extend some functionality that the stdlib exposes such as
* RandPerm
* RandIntn
* RandInt31
* RandInt63

Also added an integration test whose purpose is to be run as
a consistency check to ensure that our results never repeat
hence that our internal PRNG is uniquely seeded each time.
This integration test can be triggered by setting environment variable:
`TENDERMINT_INTEGRATION_TESTS=true`
for example
```shell
TENDERMINT_INTEGRATION_TESTS=true go test
```