If it helps:
in ESP8266 ver. 2.0.0 was added abort in
here
cores/esp8266/core_esp8266_postmortem.c:

void abort() __attribute__((noreturn));

void abort(){
    // cause exception
    s_abort_called = true;
    do {
        *((int*)0) = 0;
    } while(true);
} 

i comment the lines in MySensors/core/MyMainESP8266.cpp and it compiled ok.