This is to fix a problem noted by Eric Blake.
Code was using xfreopen to change files to binary mode, but this
fails for stdout when in append mode. Such code should use
xsetmode instead.
* NEWS: Document incompatible changes to binary-io module.
* lib/binary-io.c (__gl_setmode_check) [__DJGPP__ || __EMX__]:
New function.
* lib/binary-io.h (__gl_setmode): Rename from set_binary_mode.
(set_binary_mode): New function, which also checks for tty.
* lib/xsetmode.c, lib/xsetmode.h, modules/xsetmode: New files.