INT 31 P - DPMI 0.9+ - ALLOCATE MEMORY BLOCK
        AX = 0501h
        BX:CX = size in bytes
Return: CF clear if successful
            BX:CX = linear address of block
            SI:DI = memory block handle for resizing and freeing block
        CF set on error
            AX = error code (DPMI 1.0+) (8012h-8014h,8016h,8021h)(see AX=0000h)
Notes:  no selectors are allocated
        the memory block is allocated unlocked (can be locked with AX=0600h)
        allocations are often page granular (see AX=0604h)
SeeAlso: AX=0100h,AX=0500h,AX=0502h,AX=0503h,AX=0504h,AX=0D00h