Factor out some of the error and pool handling in the main() functions of 
svnrdump as it was done for svn/svnadmin in r1368252.

* subversion/svnrdump/svnrdump.c
  (SVNRDUMP_ERR): Remove this macro.
  (EXIT_ERROR, SVN_INT_ERR): New macros, same as those defined in
   subversion/svn/svn.c, but for svnrdump.
  (submain): Extract most of main() into this new function. Use 
   SVN_INT_ERR and EXIT_ERROR to handle errors.
  (main): Extract everything except the initialization of the application
   and of the top-level pool, and the destruction of that pool, into the
   new function sub_main(), and call that.

Patch by: Evgeny Kotkov <evgeny.kotkov{_AT_}visualsvn.com>

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1518169 13f79535-47bb-0310-9956-ffa450edef68