Fixed si, ni gdb commands (stepping)

Installation

NOTE: This module already comes preinstalled with spectranet R1003.

Upload gdbserver module

1. Go to Releases, download spectranet-gdbserver.bin file.
2. Download ethup tool for linux, mac, win32, if you haven't already.
3. Launch your spectrum (with spectranet), press the NMI button
4. Select "B", then select "A"
5. Upload the binary usint ethup: ethup <spectrum ip> spectranet-gdbserver.bin
6. Restart spectrum