RTT - data dropped when using copy paste to telnet console

[fanoush]

Hello,

looks like the RTT server code does not verify how much data was sent to 
device and simply drops received data if it does not fit into buffer on 
first try. This does work when typing slowly on keyboard but fails on 
anything faster like copy paste. If anyone is interested, my quick fix 
is available in github branch here 
https://github.com/fanoush/openocd/tree/f-rtt-server-write-retry
The windows build available there seems to work much better regarding 
this. Feel free to use that code as you wish. Unfortunately I don't have 
openocd gerrit account and don't plan to create one for such small fix 
so sorry for not creating bug report or PR.

Thanks,
fanoush