Fix a use of stack memory after function return.  Interrupting a
conflict prompt caused the pool cleanup handler to access the
stack memory that was once the terminal handle.

* subversion/libsvn_subr/prompt.c
  (terminal_open): Change parameter, allocate terminal handle here.
  (prompt, maybe_print_realm, plaintext_prompt_helper): Use allocated
   terminal handle rather than stack variable.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1443996 13f79535-47bb-0310-9956-ffa450edef68