* src/callproc.c (Fcall_process): Explicitly say that "output"
means both stdout and stderr (bug#37906).
input come from an Emacs buffer, use `call-process-region' instead.
Third argument DESTINATION specifies how to handle program's output.
+(\"Output\" here means both standard output and standard error
+output.)
If DESTINATION is a buffer, or t that stands for the current buffer,
it means insert output in that buffer before point.
If DESTINATION is nil, it means discard output; 0 means discard