Summary

• Corrected the height of the screen.
• Corrected the monitor timing to match the description in the IBM PS/55 5550-S/T/V Technical Reference.
• Added a pixel clock source for IBM 8515 monitor.
• Removed the OldLSI (DA-2) flag because I found the DA-3 has monitor detection capability and thats the difference between them.
• Changed 16/256 color mode determination to fix an issue in Windows 3.1 16 color display driver with IBM 8515 monitor.
• Fixed an issue that the color palette remains changed after Windows 3.1 restarted with 1024x768 16 color mode.

Checklist

• Closes #xxx
• I have tested my changes locally and validated that the functionality works as intended
• I have discussed this with core contributors already
• This pull request requires changes to the ROM set
  • I have opened a roms pull request - https://github.com/86Box/roms/pull/changeme/
• This pull request requires changes to the asset set
  • I have opened an assets pull request - https://github.com/86Box/assets/pull/changeme/

References

Provide links to datasheets or other documentation that helped you implement this pull request.