Update HardwareSerial.cpp
Update HardwareSerial.cpp

1) Removed Duplicate Copy and Paste from Flush Comment
2) Updated comment to "we can only transmit a maxium of 63 bytes at a time, break it up into 63 byte packets" from "we can only transmit a maxium of 64 bytes at a time, break it up into 64 byte packets"

The following changes are because the current code would seemingly only transmit 62byte packets. 
3) Changed if (size < kMaxUSBxmitPkt) to if (size <= kMaxUSBxmitPkt)
4) if (packetSize >= kMaxUSBxmitPkt) to if (packetSize > kMaxUSBxmitPkt)
adamwolf/chipKIT-core,pontech/chipKIT-core,majenkotech/chipKIT-core,chipKIT32/chipkit-core,ricklon/chipKIT-core,chipKIT32/chipkit-core,chipKIT32/chipkit-core,majenkotech/chipKIT-core,adamwolf/chipKIT-core,pontech/chipKIT-core,pontech/chipKIT-core,adamwolf/chipKIT-core,pontech/chipKIT-core,adamwolf/chipKIT-core,ricklon/chipKIT-core,chipKIT32/chipkit-core,ricklon/chipKIT-core,majenkotech/chipKIT-core,adamwolf/chipKIT-core,ricklon/chipKIT-core,majenkotech/chipKIT-core,pontech/chipKIT-core,ricklon/chipKIT-core,majenkotech/chipKIT-core,adamwolf/chipKIT-core,EmbeddedMan/chipKIT-core,EmbeddedMan/chipKIT-core,chipKIT32/chipkit-core,EmbeddedMan/chipKIT-core,adamwolf/chipKIT-core,EmbeddedMan/chipKIT-core,EmbeddedMan/chipKIT-core,majenkotech/chipKIT-core,ricklon/chipKIT-core,majenkotech/chipKIT-core,pontech/chipKIT-core,EmbeddedMan/chipKIT-core,EmbeddedMan/chipKIT-core,pontech/chipKIT-core