* remove lwip-v1.4 specific code
* ditto
* ditto
* fix ip4_addr definition
* CI: change debug builds to use IPv6, remove regular IPv6 builds
* ditto
* split pio CI in four (because they last twice the time of the other builds)
* remove option from pio
* remove lwIP-1.4 from doc
* restore pio CI splitting
* fix CI debug6 script
* ditto
* mDNS debug option + AP address is used by default when STA is also present
* mDNS: store network interface, checking it is up
* igmp: force on selected interface (avoid crash *sometimes*)
* fix for all lwip2 ipv4 ipv6 & lwip1
* mdns: IPAddress is not needed to reference associated interface
* mdns: debug: fix print warnings
* emulation: add ets_strncpy
* emulation: truly emulate AddrList (remove fake one)
Cleans up all warnings seen w/GCC 9.1 to allow it to track the main
branch more easily until 3.x.
Does not include Ticker.h "fix" of pragmas around a function cast we're
doing that GCC9 doesn't like, that will be addressed separately and
maybe only in the 3.0 branch.
Does not include GDB hook fix, either, because the pragmas required
to disable the GCC9.1 warnings don't exist in 4.8 at all.
Default interface is STA (or AP if available and STA is unavailable).
An interface can also be specified in ::begin() by its IP address.
MDNS will not cross interfaces (there is currently no notion of "bridged interfaces")
Multiple instances should be working, this is not tested in this commit.
Per 'udp_set_multicast_netif_addr()' signature and comments in lwIP sources:
An IPv4 address designating a specific interface must be used.
When an IPv6 address is given, the matching IPv4 in the same interface must be selected.
fix e3bc3c226b (r32235572)
