Add new API for opening many admin databases at once.
Add new API for opening many admin databases at once.

* subversion/libsvn_wc/wc_db.h:
  (svn_wc__db_open_many): new function

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion