Update PJNATH to the latest STUN, TURN, and ICE specs and other enhancements

[bennylp]

Currently we support:

• STUN: draft-ietf-behave-rfc3489bis-18
• ICE: draft-ietf-mmusic-ice-19.txt
• TURN: draft-ietf-behave-turn-09

STUN spec has been published as RFC 5389, while TURN spec had advanced into draft-ietf-behave-turn-13 (with major changes).

Also while we're at it, possibly add some ICE samples and more tests.

[bennylp]

In r2580:

• added IPv6 support to various STUN attributes and added the test from draft-ietf-behave-stun-test-vectors

[bennylp]

In r2589: Update TURN from draft 09 to draft 13:

• new rules for permissions:
  • permission must be created and refreshed explicitly with CreatePermission?
  • transmitting data does not refresh permission
• attributes changed/added: XOR-PEER-ADDRESS, XOR-RELAYED-ADDRESS, EVEN-PORT, DONT-FRAGMENT
• attribute(s) removed: REQUESTED-PROPS
• new status codes: 401 (Forbidden), 507 (Insufficient Capacity)
• removed status codes: 443 (Invalid IP address), 444 (Invalid Port), 508 (Insufficient Port Capacity)

[bennylp]

In r2590:

• destroy TURN session if it receives 437 (Allocation Mismatch) response

[bennylp]

In r2591:

• fixed compilation error with GNU build system due to previous TURN changes

[bennylp]

In r2592:

• initial work on an ICE demo app

[bennylp]

In r2599:

• updated ICE to issue CreatePermission before starting ICE negotiation, and to issue ChannelBind once negotiation completes and TURN candidate is used.

[bennylp]

In r2600:

• more work on icedemo sample application (more readability, some bug fixes, etc)

[bennylp]

In r2602:

• work on the CreatePermission refresh timer in the TURN client session.

[bennylp]

In r2642:

• enhance doxygen documentation for PJNATH with more content