OS_Axp, allocate explicit page

RST 20H, DEFB $D2

IN:

     IX = memory handle
     OS_Mal supplies the BH[L] address page

     Fc = 0, OK

     Fc = 1
          A = RC_FAIL, failed to allocate memory

     ..BCDEHL/IXIY same
     AF....../.... different

Internal operating system usage.
Interlogic comment: We believe that OS_Mal uses this call to
allocate new pages in a pool when needed. Since page are on 256 byte
boundaries the L register is probably ignored by this call.