Remove O_RDONLY, O_WRONLY definitions, not needed.

Remove O_RDONLY, O_WRONLY definitions, not needed.
* src/unexcoff.c:
* src/lread.c:
* src/fileio.c:
* src/doc.c:
* src/callproc.c:
* src/alloc.c:
* src/termcap.c: Remove O_RDONLY O_WRONLY definitions.