set_file_pointer and 64 bit file access

[Bill Medland]

I see we are in the middle of converting set_file_pointer towards 64 bit
file systems.  Currently the code is confused as to when to change from
unsigned to signed int for the low 32 bits.  Should it happen in
SetFilePointer before sending the request (which means we end up changing
the request format) or should it happen within set_file_pointer (after
changing the argument back to a signed int; this would also require work in
SetFilePointer to get it to set up the request correctly).

Any views?

Bill