nway_mergesort optimizations: use temporary buffer instead of an array of default-constructed values. Use move constructor instead of copy constructor in C++11 for moving values from a temporary buffer into sorted array
nway_mergesort optimizations: use temporary buffer instead of an array of default-constructed values. Use move constructor instead of copy constructor in C++11 for moving values from a temporary buffer into sorted array

valyala/gheap,valyala/gheap