Improvements to the monitor and matrix mode

[Paul Gardner-Stephen]

Hi all,

Just a heads up that a number of improvements and fixes have been incorporated into the matrix mode / monitor interface, including the following.

Much of this builds on a pile of work that Kenneth did to re-implement the monitor interface in a way that uses less of the FPGA, but is more functional, as well as saving FPGA space in various other places, to make sure that everything fits fine. We are very appreciative of his work to achieve this.

1. When "matrix mode" is activated via C= + TAB (or C= + <- on a C64 keyboard), the serial port is cut off, to ensure security when interacting locally.

2. Various display glitches have been fixed, and short of one remaining minor issue, the matrix mode interface to the monitor now works correctly.

3. F1 and F3 can be used to page through memory in the monitor when in matrix mode.  The DELETE key and SHIFT-HOME also work as expected, to provide a convenient experience.

4. The d/D command now displays a disassembly of the contents of memory.

5. The m/M command works as before, but to fit in the 50-column display of the matrix mode, whitespace between bytes in memory output has been replaced by alternating the colour of each column of bytes.

6. Very many other small and large issues.

The monitor_load and monitor_save programs have been updated to reflect the changed formatting of various outputs from the monitor. 

The m65dbg program will require similar updating.  If someone is willing to test m65dbg with the head of the sept18 branch of mega65-core, this would be appreciated.  Once that has been done, and assuming no one turns up any horrible problems, we will push the sept18 branch up onto development and master in the near future.

Paul.