Dump out malloc heap in a range of addresses, showed allocated/free blocks.
sheap START-ADDR [END-ADDR]
will dump out free and allocated malloc blocks within the given address
range.  If not given, END-ADDR is taken to be 1024 bytes after START-ADDR.
Caveats: It is not possible to reliably identify allocated memory blocks.
         Dumping will start at the first free block found within
         the given range, if any.
         This only works with the GNU libc malloc, not with any
         alternative allocators (tcmalloc, etc).
 
Definition at line 75 of file sheap.py.