doc: improve doc about ioctl

[Bruno Haible]

A small doc update:


2017-10-10  Bruno Haible  <address@hidden>

        doc: Improve doc about ioctl.
        * doc/posix-functions/ioctl.texi: Fix list of platforms with non-POSIX
        prototype.

diff --git a/doc/posix-functions/ioctl.texi b/doc/posix-functions/ioctl.texi
index c4e2415..e4a1dde 100644
--- a/doc/posix-functions/ioctl.texi
+++ b/doc/posix-functions/ioctl.texi
@@ -13,8 +13,9 @@ On Windows platforms (excluding Cygwin), @code{ioctl} is 
called
 @code{ioctlsocket}, and error codes from this function are not placed in
 @code{errno}, and @code{WSAGetLastError} must be used instead.
 @item
-On glibc platforms, the second parameter is of type @code{unsigned long}
-rather than @code{int}.
+The second parameter is of type @code{unsigned long} rather than @code{int}
+on some platforms:
+glibc 2.26, Mac OS X 10.5, FreeBSD 11.0, NetBSD 7.0, OpenBSD 6.0, BeOS.
 @end itemize
 
 Portability problems not fixed by Gnulib: