Fix the problem where simply hitting 'enter' at the interactive conflict
prompt would postpone conflicts instead of responding with "unknown option".

* subversion/svn/conflict-callbacks.c
  (text_conflict_options): Options with code "" are special. They indicate
   where blank lines should be placed in the conflict prompt, and should not
   be used when evaluating answers given by the user. So initialise their
   choices to 'unspecified', instead of leaving them initialised to zero.
   A value of zero maps to the 'postpone' choice when passed back to the
   Subversion libraries. Passing 'unspecified' back into the library will
   raise an error instead. This doesn't actually fix the problem but makes
   the special case of "" stand out better.
  (find_option): Just like in help_strin(), we must special-case answers
   using option code "" because they do not correspond to any valid answer.
   This fixes the issue where just hitting enter didn't result in an "unknown
   option" response.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1449655 13f79535-47bb-0310-9956-ffa450edef68
* subversion/svn/svn.c
  (sub_main): If some operation fails with SQLITE_BUSY, wrap the error in a
   message that hings at possible causes, such as other long-running processes
   or missing locking support on network filesystems. This should help some
   users with fixing the problem on their own.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1449659 13f79535-47bb-0310-9956-ffa450edef68