Cleanups:
o Clean up data types and make sure they cannot overflow. (size_t vs. u64 vs. sh_off_t vs. uns)
+o Clean up log levels.
+o Clean up introductory comments.
o Log messages should show both original and new size of the data. The speed
should be probably calculated from the former.
o Automatically tune ASORT_MIN_RADIX, ASORT_MIN_SHIFT and especially ASORT_RADIX_BITS.
-o Check undefs in sorter.h and array.h.
+o Buffer sizing in shep-export.
Improvements:
o Switching between direct and normal I/O. Should use normal I/O if the input is small enough.