1) I corrected a bug with the silo reader that caused "_meshtv_searchpath"
   to be ignored. I also added support for reading "_visit_searchpath" as a
   synonym for "_meshtv_searchpath". This resolves #2401.

2) I added the utility "add_visit_searchpath" that adds a "_visit_searchpath"
   to the root directory of a Silo file. Its usage is:

   ./add_visit_searchpath filename <searchpath>

   If the searchpath is not specified then an empty search path is added,
   causing VisIt to only look for variables at the root level of the Silo
   file. This resolves #2402.



git-svn-id: http://visit.ilight.com/svn/visit/trunk/src@27371 18c085ea-50e0-402c-830e-de6fd14e8384