This CL makes the following changes to RangeSet:
- Uses std::pair<size_t, size_t> to represent a Range;
- Uses std::vector<Range> to represent a RangeSet;
- Provides const iterators (forward and reverse);
- Provides const accessor;
- 'blocks()' returns the number of blocks (formerly 'size');
- 'size()' returns the number of Range's (formerly 'count').
Test: recovery_unit_test
Test: Apply an incremental update with the new updater.
Change-Id: Ia1fbb343370a152e1f7aa050cf914c2da09b1396
bf5b77dbf7