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.

Build.sh

@@ -1668,6 +1668,7 @@ ac_header sys/select.h sys/types.h
 ac_header sys/sysmacros.h
 ac_header bstring.h
 ac_header grp.h sys/types.h
+ac_header io.h
 ac_header libgen.h
 ac_header libutil.h sys/types.h
 ac_header paths.h