None of the other ports do, since introduction of mp_state_ctx_t. In
the case of current esp8266 port, heap is inside BSS, so scanning it
picked up a lot of dead pointers.
As user_init() is not a true main functions, the stack pointer captured within
is not pointing at the base of the stack. This caused gc_collect being called
with sp being higher than stack_end, causing integer overflow and crashing as
gc tried to scan almost the entire address space.
