INT 21 P - FlashTek X-32VM - ALLOCATE PROTECTED-MODE SELECTOR
AX = 3501h
Return: CF clear if successful
BX = new selector
CF set on error (no more selectors available)
Note:   the new selector will be an expand-up read/write data selector with
undefined base and limit
SeeAlso: INT 31/AX=0000h

See also: 213502

213501 - FlashTek X-32VM - ALLOCATE PROTECTED-MODE SELECTOR