first key byte and writing to a temp file, then sorting the records from
each temp file that had the same first key byte (and repeating for upto
4 key bytes) was a nice idea, but completely doomed to failure.
Eg PR/9308 where a 70MB file has all but one record the same and short keys.
Not only does the code not work, it is rather guaranteed to be slow.
Instead always use a merge sort for fully sorted chunk of records (each
temporary file contains one lot of sorted records).
The -H option already did this, so just rip out all the code and variables
that can't be used when -H was specified.
Further cleanup to come ...
f155f3b8b9