- add large file support
- tested on 64bit openSUSE using LDFLAGS=-m32 CFLAGS=-m32 ./configure
- corrected signed-ness of off_t and add size_t smarts
- change a bunch of other types to ssize_t/off_t/size_t
- change simple_itoa to use a size_t
fix typo
- check for and use pread if available, otherwise use our implementation.  This
  obviates the need to seek around all the time, and pread is fast and
  supported on most systems.
- fix --disable-mmap and make sure to re-run autoheader, otherwise pread
  won't ever get used