Make "rm --interactive=never ..." never prompt.
* NEWS: Mention this.
* src/remove.h (enum rm_interactive): New ternary type.
(struct rm_options) [interactive]: Use it, here -- rather than bool.
* src/remove.c (prompt): Reflect type change.
* src/mv.c (rm_option_init): Initialize to RMI_NEVER now.
* src/rm.c (main): Add a FIXME comment for '-d' option.
Adapt to type change of rm_options.interactive.
* tests/rm/i-never: New file. Test for the above fix.
* tests/rm/Makefile.am (TESTS): Add i-never.