Split the merge sort so that fsort() can pass the 'FILE *' of the temporary
files to be merged into the merge code.
Don't rely on realloc() not moving the end address of a buffer!
Rework merge sort so that it sorts pointers to 'struct mfile' and only
copies about sort record descriptors.
No functional change intended.
an array of 'RECHEADER *' and remove all the crappy stuff that backed up
by REC_DATA_OFFSET (etc).
Also change radix_sort() to return the number of elements, soon to be used
to drop duplicate keys (for sort -u).
Simplify logic for reading input records.
Do a merge sort whenever we have 16 partial sorted blocks.
The patient is breathing, but still carrying a lot of extra weight.
if needed and record count is within bounds (<MAXNUM), rather than
sorting the input by 64KB chunks. This cuts the number of needed
temporary files considerably (and improves performance, too).
Slighly adjust some #defines, mostly to power of 2 values.
This addresses bin/12673 and bin/12614, as well as complains from other
people.
