BIND 10 #2088: introduce MemorySegment class

[BIND 10 Development]

#2088: introduce MemorySegment class
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  medium        |                    Milestone:  Next-
           Component:  data source   |  Sprint-Proposed
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:  in-
         Total Hours:  0             |  memory NSEC
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 We'll use this so we can use various types of memory segment ('local',
 'shared memory', 'mmap) transparently.

 - define an abstract base class.  We only need the simplest allocator
   and deallocator:
 {{{#!cpp
   void* allocate(size_t size);
   void deallocate(void* ptr, size_t size);
 }}};
   (note: the size parameter is not mandatory functionality-wise, but
    we'll need this if we want to detect memory
   it'd also be better to have "allMemoryDeallocated" for memory leak
   detection
 - define and implement LocalMemorySegment derived class.
   It internally uses malloc/free or new/delete.  not sure this
   should be a "nothrow" version (probably not, but think about it)

 No dependency.  Can start anytime.

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Ticket URL: <http://bind10.isc.org/ticket/2088>
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