Thanks for the hint I needed to discover the obvious. It worked for me only
because pthreads had not been built yet! After doing so, it the vmime failed
for me just as it did for Volker.
I think the solution is in the attached patch. See embedded commit message.
Could you please try it?
That seems to have fixed it and it builds successfully now. However, I
thought the idea was to disable pthreads for vmime and the fix would
be to patch configure to not detect it. I was trying to wrap an
AC_ARG_ENABLE around the ACX_PTHREAD macro (configure.in:527) but
didn't get very far.