initial djgpp port:
- use findfirst() instead of stat() for dos in file_io.
- always use O_BINARY in file open flags, which removes a few ifdefs
  from the body of the code. define it as 0 if not already defined.
- make the lock functions nop for dos builds.
- combine some _WIN32 conditionals with __DJGPP__ where appropriate.
  complete some other missing pieces for djgpp.
add djgpp-specific makefile and config.
djgpp port: add a minimalistic README, and a minor edit to the Makefile.
Merge pull request #28 from sezero/djgpp

initial dos (djgpp) port by sezero