Update libavoid, libcola and libvpsc code

[jazzynico]

Follow-up to Bug #1155046 (Assertion `pathlen < 200' failed).

The Libavoid code embedded in the Inkscape code is quite old (connector.cpp is from 2009), and the upstream project is still alive as part of the Adaptagrams project (https://github.com/mjwybrow/adaptagrams).

It would be interesting to update our version as it probably fixes some connectors bugs.

[jazzynico (jazzynico)]

While we're at it, we could also update Libcola (also in https://github.com/mjwybrow/adaptagrams).

[Alex Valavanis (valavanisalex)]

As usual, the first step is a bit of archaeology... we need to identify:

1. The commit in the Adaptagrams repo at which we forked the code
2. The list of changes we have made since then:
2a. Which of these are minor/cosmetic (e.g., fixes for relatively harmless compiler warnings)?
2b. Can any patches be forwarded upstream?
2c. Do we need to maintain any Inkscape-specific patches?

[jazzynico (jazzynico)]

Some useful links:
* Last libavoid revision ported to Inkscape:
https://github.com/mjwybrow/adaptagrams/commit/412cfdfe87db311125eeef14c2c787ca2521f5ea (Commits on Sep 16, 2009)
* Last libcola revision ported to Inkscape:
https://github.com/mjwybrow/adaptagrams/commit/d807d1b9835880f0eb3143575857d8dcb1e54059 (Commits on Jul 17, 2006)

Of course libavoid and libcola changed a lot in Inkscape and upstream...

[jazzynico (jazzynico)]

And we also need to update libvpsc...

[jazzynico (jazzynico)]

Another related report: bug #1675779 "connector movement crash inkscape" (https://bugs.launchpad.net/inkscape/+bug/1675779).

[Mc (mc...)]

Maybe we can ask the adaptagrams author ? (if i'm not mistaken, he was the one implemetning it into inkscape)

[Sylvain Chiron (frigory)]

I’ve submitted a merge request for this bug:
https://gitlab.com/inkscape/inkscape/merge_requests/29

[Alex Valavanis (valavanisalex)]

Merged to master, 2017-07-01