Read in text mode, write in binary mode on OS/2

This enables to convert CR+LF to LF when reading, but disables to
convert LF to CR+LF when writing.

Instead, however, CR+LF are not passed into mksh as is.

sh.h

@@ -64,6 +64,9 @@
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
+#if HAVE_IO_H
+#include <io.h>
+#endif
 #if HAVE_LIBGEN_H
 #include <libgen.h>
 #endif