xfree86: Undocument UseSIGIO in xorg.conf

The doc text is wrong at this point, input processing isn't going to
vary based on this, so we shouldn't say it does. The only thing this
_does_ get used for is DRI1 SwapBuffers (on everything but savage), and
if you disable it you're not going to get DRI1 at all, so we really
shouldn't even mention it.

Still, leave the option wired up to the parser so we don't break any
DRI1-driver-using setup relying on it being disabled, and so we don't
complain about unused options elsewhere.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Acked-by: Keith Packard <keithp@keithp.com>

hw/xfree86/man/xorg.conf.man

@@ -511,15 +511,6 @@ core file.
 In general you never want to use this option unless you are debugging an Xorg
 server problem and know how to deal with the consequences.
 .TP 7
-.BI "Option \*qUseSIGIO\*q  \*q" boolean \*q
-This controls whether the Xorg server requests that events from
-input devices be reported via a SIGIO signal handler (also known as SIGPOLL
-on some platforms), or only reported via the standard select(3) loop.
-The default behaviour is platform specific.   In general you do not want to
-use this option unless you are debugging the Xorg server, or
-working around a specific bug until it is fixed, and understand the
-consequences.
-.TP 7
 .BI "Option \*qDontVTSwitch\*q  \*q" boolean \*q
 This disallows the use of the
 .BI Ctrl+Alt+F n