* ifndef'd LWIP_OPEN_SRC to prevent a redefined warning
* ABORT on NOTIFY to prevent responding to NOTIFY messages (we should only respond to M-SEARCH messages)
* case-insensitive compare of _deviceType to enable response to all-lowercase Alexa queries (robustness principle)
Previously, the notify template and and response templates had a
hardcoded NT (or ST) of upnp:root device. They now include the
deviceType that is set in initialization.
also a small formatting fix. this should now allow the system to
actually respond to SSDP discoveries that are issued on the network ...
i'm still not 100% certain if this is right due to the way that the
switch() statement is setup; it could be processing more than it should
* can now specify the TTL programmatically
* can now define the device type urn (up to 64 chars)
** still defaults to `Basic:1`
* can now set the serial number using a `uint32_t`, formatted as %08X
