AH = D5h: Get Bitmap Data Status

This function returns global information about the currently loaded Bitmap tables.

• Input: AH = D5h.

• Output: AX = ID of Bitmap on top of BMSTK
  BX = ID of Currently Active Bitmap
  CX = Sum (Logical OR) of ID's of all Currently Loaded Bitmaps
  DX = Available Memory in Bit Map Buffer (Bytes)
  

• Registers modified: AX, BX, CX, DX, FLAGS
• Error conditions: None