Also reduces the IRAM footprint of the fatal exception handler, as only the prelude (which disables interrupts & enables the flash mapping) is in IRAM now. Closes #54, relevant to #133.
As per mbedtls documentation. This is different to lwip_getaddrinfo() which uses loopback for a NULL address. Fixes bug mentioned here https://groups.google.com/forum/#!topic/esp-open-rtos/3KH5TZSTMUw