Update to LWIP 2.1.2

[tymoteuszblochmobica]

Description

Latest LWIP 2.1.2 with necessary patches integrated with MbebOS

Pull request type

[ ] Fix
[ ] Refactor
[ ] Target update
[x ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

Reviewers

@SeppoTakalo
@mikaleppanen
@kjbracey-arm

Release Notes

Latest LWIP 2.1.2 released is now integrated with MbedOS.
New LWIP release has improvements in following areas:

-IP4 routing
-IP6 scopes and zones
-dhcp6
-nd6
-tcp
-Sockets
-Binding network interfaces to sockets

LWIP changelog contains detailed changes

MbedOS dedicated patches were applied to new LWIP.
Multihoming was refactored due to new socket-interface bind implementation.

[ciarmcom]

@tymoteuszblochmobica, thank you for your changes.
@SeppoTakalo @kjbracey-arm @mikaleppanen @ARMmbed/mbed-os-test @ARMmbed/mbed-os-ipcore @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

Second commit is only about "Multihoming was refactored due to new socket-interface bind implementation." ?
The commit changes lot of files (adding parameters, new functions) so not certain what is this refactor doing - would it make sense to add there more details or split ?

[michalpasztamobica]

@0xc0170 , I think the most important reviews are still to come from @mikaleppanen , @kjbracey-arm and @SeppoTakalo . Please do not merge until at least one of them approves...

Regarding the commit split, the idea was the following:

1. Commit the actual new LWIP.
2. Get multihoming working again.

The second commit message body is "Multihoming fixed according to new LWIP implementation." Perhaps this should become the title of the commit message instead of just being its body?

[0xc0170]

@0xc0170 , I think the most important reviews are still to come from @mikaleppanen , @kjbracey-arm and @SeppoTakalo . Please do not merge until at least one of them approves...

👍

The second commit message body is "Multihoming fixed according to new LWIP implementation." Perhaps this should become the title of the commit message instead of just being its body?

Could be. Let other reviewers look at this as well

[SeppoTakalo]

Looks OK.

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts

[cmonr]

Info: This PR has now been rebased.

Travis CI did not want to start, so I gave the PR an updated sha to generate the webhook.

[cmonr]

CI started

[mbed-ci]

Test run: FAILED

Summary: 1 of 11 test jobs failed
Build number : 2
Build artifacts

Failed test jobs:

• jenkins-ci/mbed-os-ci_exporter

[0xc0170]

Exporters restarted - internal symlink error