INT 21 Pu - Phar Lap 386/DOS-Extender - GET PAGE TYPES
        AX = 252Bh
        BL = 04h
        ???
Return: ???
Note:   returns one word per page

Bitfields for page information:
 bits 3-0       page type
        0 unmapped
        1 allocated
        2 physical device page
 bit 4  locked
 bit 5  swapped to disk
 bit 6  mapped to read-only data file
 bit 7  mapped to read/write data file

.