It is that maybe less modification working on the components is better, so I just modified the platform
code of AES, SHA and so on.
ESP8266 has no real hardware AES, SHA or bignum peripheral, but some method can speed up the process of part
of upper algorithm, so I also added the platform code of AES, SHA, bignum, ARC, MD5.
ESP8266 has no platform of bignum, so users should not enable the bignum hardware at "menuconfig".
1. wpa_supplicatn use extra SHA default
2. mbedtls use extra SHA default
3. bootloader use extra SHA default
4. user code can use extra SHA default
Above all, using unified module is easy to maintenance code and save rom or ram.