vchoi_fork

[svn-r5407] Purpose:
    Bug fix
Description:
    Was not able to handle data size (file size) larger than 32bits.
    Was using long, which is only 4 bytes big in SP, thus overflowing
    into negative when trying to address 2GB or larger.
Solution:
    Changed those variables involved in file size/offset calculation
    to type off_t.  (If a certain system/compiler has off_t defined
    as 4 bytes, it can't write to file size larger than 2GB anyway.)

    Note that the lseek of SP with -D_LARGE_FILE still fails for
    offset larger than 2GB (works for 2GB).  That has to be fixed
    soon.
Platforms tested:
   burrwhite (linux 2.4) and modi4 parallel.