dovecot, configure and documentation as hardstop

Hi,

As preparations for a port to AIX - making sure I can get it to build on linux with gcc. While it is fairly easy to add the requirements (on GNU Linux) having pandoc as a configure "hardstop", even with --without-docs or --with-docs=no is a bit worrisome as I am fearful that I amy not be able to get pandoc ported as well.

Hence a request that a missing pandoc become a warnig, and just not done when pandoc is not available, or at least accept one of --without-docs and --with-docs=no (or should I be using --with-pandata=no? )

Michael