Uninitialized pointer in scp can cause access violation.

More MTABs that count on scp's former misuse of pstring.  Changed them to mstring as intended/required.
Merge branch 'master' into KDP
Make show iospace output straight columns when behind UBAs.

The previous show iospace assumed octal address widths, and vectors that were three digits wide.

This isn't true when behind a VAX UBA.  Addresses are hex; vectors can be 4 digits.

This edit teaches show iospace to calculate column widths and label positioning based on what the machine actually outputs.
Merge branch 'master' into KDP