bug#24051: 24.5; doc of `external-debugging-output'

[Drew Adams]

1. Please consider documenting this in the Elisp manual, e.g., where we
document `print'.

2. The doc string should enclose "print" in `...':

 Write CHARACTER to stderr.
 You can call `print' while debugging emacs, and pass it this function
 to make it write to the debugging output.


In GNU Emacs 24.5.1 (i686-pc-mingw32)
 of 2015-04-11 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/usr --host=i686-pc-mingw32'