DiagROM Improvements

Some particularly vexing Spectrum hardware faults lately have led to improvements to my DiagROM program. It now attempts to detect faults with the 74LS157 multiplexors which can falsely suggest RAM is faulty. There is a also an upper RAM scanner that shows the RAM as a bitmap window, allowing visual inspection of its content – a picture is worth a 1000 words after all! The latest version is in my SMART Card software archive.