Wrong platform check for Xinerama support

[Lionel Elie Mamane]

On Thu, Jan 03, 2013 at 09:12:12AM +0200, Tor Lillqvist wrote:

>> if test "$_os" = "Linux" -o "$_os" = "FreeBSD" -o "$_os" = "MirBSD" -o "$_os" = "OpenBSD" #etc, etc;
>>    UNIX_X11=true || POSIX_OS=true
>> fi
>>
>> and then test UNIX_X11 (or POSIX_OS).

> I doubt we need any separate flag for POSIXness, because basically
> anything that isn't Windows is "POSIX", surely.

And even Windows NT has a POSIX layer... OK, then "POSIX_OS" is not
the right name choice for what I want this variable to mean. UNIX_X11
is maybe the better name.

-- 
Lionel