This introduces the concept of ext (external/extended) arguments per
tcp_pcb (also for listening pcbs) to store more data than just one
"void *arg" per pcb. The "arg" is for use to applications, whereas
the ext_args may be used by frameworks and leave "arg" untouched.
In addition to a void pointer, callbacks are added to help frameworks
migrate arguments from listen pcb to connection pcb and to free args
when the pcb is freed.
Signed-off-by: goldsimon <goldsimon@gmx.de>
0e85582bc0