Currently, LwIP segment retransmission time is 12, which is very long
time as each timeout doubles the retransmission timeout.
Make that to 6 as that is same what we use in Nanostack.
For speeding up of LWIP in RZ/A1, I added four new config processes in mbed_lib.json and lwipopts.h, overriden those values.
Since RZ/A1 incorporates a large memory, can actualize speeding up by running with the override value.
Also those new config processes will be helpful for more customize.
Seppo Takalo
Tymoteusz Bloch
Martin Kojtal
TomoYamanaka