Free Memory Block

Frees a memory block that was previously allocated with
either the Allocate Memory Block function (Int 31H Function
0501H) or the Allocate Linear Memory Block function (Int 31H
Function 0504H).

Call With:

   AX     = 0502H
   SI:DI  = memory block handle

Returns:

   if function successful
   Carry flag= clear

   if function unsuccessful
   Carry flag= set
   AX     = error code
           8023H   invalid handle

Notes:

o  This call will correctly free all of the possible page
   types that can occur in a memory block: committed pages,
   uncommitted pages, and mapped pages (see Appendix A:
   Glossary).

o  No descriptors are freed by this call.  It is the
   client's responsibility to free any descriptors that it
   previously allocated to map the memory block.
   Descriptors should be freed before linear memory blocks.