Delete unused spreadsort implementation.

webrtc/system_wrappers/source/spreadsortlib/constants.hpp

-/*Boost Software License - Version 1.0 - August 17th, 2003
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-#ifndef BOOST_SPREADSORT_CONSTANTS
-#define BOOST_SPREADSORT_CONSTANTS
-namespace boost {
-namespace detail {
-//Tuning constants
-//Sets the minimum number of items per bin.
-static const unsigned LOG_MEAN_BIN_SIZE = 2;
-//This should be tuned to your processor cache; if you go too large you get cache misses on bins
-//The smaller this number, the less worst-case memory usage.  If too small, too many recursions slow down spreadsort
-static const unsigned MAX_SPLITS = 10;
-//Used to force a comparison-based sorting for small bins, if it's faster.  Minimum value 0
-static const unsigned LOG_MIN_SPLIT_COUNT = 5;
-//There is a minimum size below which it is not worth using spreadsort
-static const long MIN_SORT_SIZE = 1000;
-//This is the constant on the log base n of m calculation; make this larger the faster std::sort is relative to spreadsort
-static const unsigned LOG_CONST = 2;
-}
-}
-#endif