INT 2F - PCIBM PC DOS 5.0+ KEYB.COM - SET KEYBOARD SUB-MAPPING
AX = AD84h
Return: if KEYB is in foreign mode:
AL = current layout
00h primary layout
01h secondary layout
Note: This function is not supported by MS-DOS 5 - 7.10.
SeeAlso: AX=AD85h,AX=AD82h