Revision 1822401

Fix a 'dereference pointer to the wrong object' crash in the conflict resolver.

* subversion/libsvn_client/conflicts.c
  (configure_option_incoming_move_file_merge,
   configure_option_incoming_dir_merge): The tree_conflict_incoming_details
    pointer does not necessarily point to a data structure of type struct
    conflict_tree_incoming_delete_details. E.g. in case of incoming edits
    it will point to an apr_array_header_t.
    Only cast this pointer to struct conflict_tree_incoming_delete_details
    if the incoming change is in fact a deletion. Otherwise, we can crash
    since struct conflict_tree_incoming_delete_details (72 bytes) is larger
    than apr_array_header_t (32 bytes), and a read of the larger type through
    this pointer could run into unmapped address space.
    Generally, accessing one type of object through another type of pointer
    is undefined behaviour.

Found by: svn-bb-openbsd buildbot
Discussed with: brane