Reduce wait time in dwReadBytes to boost transfer rate from 160Bps to 487Bps

[DeqingSun]

There used to be a 30ms interval between 2 debugWIRE access.

It seems dwReadBytes wait 23ms after receiving the last byte.

So I added a test in dwReadBytes, if the coming byte is not the 1st one, it will only wait for about 1 Byte's time.

At this moment, the interval between 2 debugWIRE access reduced to 6ms.

[DeqingSun]

Now the branch has been both tested in OSX 10.13 and Win7