PDP11/VAX: Detect vector conflicts, SHOW IOSPACE and SHOW DEVICE improvements

From Timothe Litt:
  - Detect vector conflicts, SHOW IOSPACE
  - Detect conflicting vector assignments.
  - Correct show iospace display of high vector for multi-unit devices
  - Display vectors in DEV_RDX in show iospace
  - Ignore disabled devices when searching for conflict.
  - Improve device conflict reporting, Report both devices when address conflict is detected.

From Mark Pizzolato:
  - Added optional alternate radix output display for device address and vector values
    displayed by SHOW DEVICE.
    -H and -O switches select hex or octal output in addition to the default radix displayed
    by the normal simulator.
Merge branch 'master' of github.com:simh/simh