X11R7 on amd64: Undefined PLT symbol "_XGetRequest" (symnum = 99)

[steve%prd.co.uk@localhost (Steve Blinkhorn)]

This problem has plagued me since I moved to 7.0 on amd64 from 5.x
on i386, and I can't get any traction on it from scanning various
sites where the same or very similar reports are to be found.

"/usr/X11R7/lib/libXext.so.7: Undefined PLT symbol "_XGetRequest" (symnum = 99)"
prevents me from using libreoffice5 and firefox-59.0.2 to name two
packages I would otherwise use on a daily basis, but there are
several others I have tried with the same outcome.   For a long
time I thought the problem was because I mostly work over vnc, and
that maybe I needed to move from vanilla vncserver to tigervnc.
But tigervnc built locally has the same problem.

So I set up a machine with a directly-connected console using stock
X11 from the 7.0 distribution - same problem.   I can't believe I'm
the only person to run into this, so either I'm too dumb to recognise
something obvious to most, or I'm just no using the right search terms
to identify the issue.

-- 
Steve Blinkhorn <steve%prd.co.uk@localhost>