[PATCH for server-1.16-branch] Add -iglx & +iglx to Xserver.man

[Alan Coopersmith]

Covers the current state after commits 99f0365b1fbdfd9238b9f,
d0da0e9c3bb8fe0cd4879, & e3aa13b8d63ea2fba6eb4 were all applied.

Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
Reviewed-by: James Jones <jajones at nvidia.com>
Reviewed-by: Robert Morell <rmorell at nvidia.com>
Signed-off-by: Keith Packard <keithp at keithp.com>
(cherry picked from commit b09d59342804db7dbb8056dca43dd39f54e290aa)

Modified for server-1.16-branch to show +iglx as default instead of -iglx,
to match code in os/utils.c in server-1.16-branch.
---
 man/Xserver.man |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/man/Xserver.man b/man/Xserver.man
index 7a74e85..a4097ad 100644
--- a/man/Xserver.man
+++ b/man/Xserver.man
@@ -181,6 +181,16 @@ prints a usage message.
 .B \-I
 causes all remaining command line arguments to be ignored.
 .TP 8
+.B \-iglx
+Prohibit creating indirect GLX contexts.  Indirect GLX is of limited use,
+since it lacks support for many modern OpenGL features and extensions;
+it's slower than direct contexts; and it opens a large attack surface for
+protocol parsing errors.
+.TP 8
+.B +iglx
+Allow creating indirect GLX contexts.
+This is the default unless \-iglx is specified.
+.TP 8
 .B \-maxbigreqsize \fIsize\fP
 sets the maximum big request to
 .I size
-- 
1.7.9.2