xfce: missing dependency on xpm

[Albert Kinderman]

While making xfce in ports (cvsup update last night), the configure 
failed with

checking for XpmReadFileToXpmImage in -lXpm... no
configure: error: libXpm not found
===>  Script "configure" failed unexpectedly.

Installing /usr/ports/graphics/xpm allows the xfce port to make and 
install properly.

-- 
Albert Kinderman     California State University, Northridge
       Department of Systems and Operations Management