described here: https://github.com/ipfs/team-mgmt/issues/849

This series of commits aims to update go-ipfs to follow a dual-licensing best practice based on research into open-source licensing by @ianjdarrow. He recommends a dual MIT and Apache 2.0 license -

> This has two major benefits:

> - There are concerns in the open source community about whether the MIT license leaves users vulnerable to patent infringement claims. We think the pure legal risk is small, but the way the open source community interacts with our project is really important. It makes sense to pick the license that makes the largest number of people comfortable.
- There's now no reason to adopt a separate DCO, since the Apache-2 license grant addresses the same issue.

> Why use a dual license, instead of just Apache-2? The Apache-2 license is incompatible with the GPLv2 license, which includes things like the Linux kernel. With a dual license, GPLv2 projects can just use the MIT license instead. Our goal is to make our software available to as many projects as possible, so we'd rather adopt a licensing scheme that doesn't exclude anyone.

In addition to these commits, we also need to get an explicit OK from current and past contributors to give their consent to relicensing - which will happen in an issue thread.

Go test fix

In TestExternalUnmount, the Mount function is called which returns an
error which can be nil. The error type is then used in a comparison
where Error() is called on it. If the error is nil, this results in a
panic.

Added a if err != nil {} guard to make sure that Error() is not called
if the value is nil
 On branch go-test-fix
 Changes to be committed:
	modified:   fuse/node/mount_test.go
License: MIT
Signed-off-by: Chris Buesser <christopher.buesser@gmail.com>

This commit fixes the errors resulting from passing a nil pointer to the
core.NewNode function in TestExternalUnmmount and setupIpnsTest.

In the previous nil's place a &core.BuildCfg{} is now passed.

Both changes follow the same pattern:

```diff
-  node, err = core.NewNode(context.Background(), nil)
+  node, err = core.NewNode(context.Background(), &core.BuildCfg{})
```

 On branch go-test-fix
 Changes to be committed:
	modified:   fuse/ipns/ipns_test.go
	modified:   fuse/node/mount_test.go
License: MIT
Signed-off-by: Chris Buesser <christopher.buesser@gmail.com>

commands(pin update): return resolved CIDs instead of paths

core: fix autonat construction

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

Test and fix GC/pin bug

License: MIT
Signed-off-by: Erik Ingenito <erik.ingenito@protocol.ai>

dep: update go-ipfs-config

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

fixes #6284

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

GOCC implementation & fix in make & build scripts

The usage of a native 'go' command has been replaced with a make &
environment variable $GOCC. This enables building with multiple go
versions on a single machine as documented:
  * https://golang.org/doc/install#extra_versions

This enables the usage of:
```bash
$ make install
$ # OR
$ GOCC=go1.12.3 make install
$ # OR
$ GOCC=go1.12.4 make install
```
And the build and test tools now pick up on this change

 On branch go-version-check
 Changes to be committed:
	modified:   Rules.mk
	modified:   bin/check_go_version
	modified:   bin/dist_get
	modified:   bin/maketarball.sh
	modified:   coverage/Rules.mk
	modified:   mk/golang.mk
	modified:   mk/tarball.mk
License: MIT
Signed-off-by: Chris Buesser <christopher.buesser@gmail.com>

gc: cancel context

We were canceling the context in `GarbageCollect` but some functions call `GC`
directly. Move the context cancelation down to where we actually _need_ it.

fixes #6279

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

dep: update multistream

Reduce lock contention

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

fix: windows friendly daemon help

tweak the daemon --help output to use escaped double quotes instead
of single quotes so the same command can be used on windows.

fixes: #2034

License: MIT
Signed-off-by: Oli Evans <oli@tableflip.io>

Invert constructor config handling 

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

fixes #6269

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

docs: document environment variables

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

dep: update go-libp2p

1. Reduces lock contention in the peerstore.
2. Fixes an ancient secio bug.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

dep: drop leb.io/hashland

add: Return error from iterator

License: MIT
Signed-off-by: Łukasz Magiera <magik6k@gmail.com>

Instead, golang's keccak and spaolacci's murmur3 (both of which are maintained).

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

fixes #5828

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

dep: update many

* go-ipfs-files: fixes some bugs with WebFile.
* go-unixfs: update murmur3.
* go-libp2p-connmgr: update for peer protection feature.
* base58: reduce allocations from 3 to 2.
* golang.org/x/...: upstream updates.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>