Mono issue.

[Miguel de Icaza <miguel ximian com>]

Hello guys,

   There is an issue with Mono embeddability as a plug-in, apparently
(and we have not yet confirmed this, but there is some evidence towards
this), the GC system can not be dynamically loaded into an application. 
So this might be an issue to consider.

   If we make the plugin conditional, we could just as well make the
gnumeric build conditional on this.  Thoughts?

Miguel.