Fix evil copy-mode - #670

Entering copy or Emacs mode from evil insert state left insert state
active.  Insert state binds no printable keys, so j, k and other
motions hit the read-only fast-exit map, leaving copy mode and typing
the letter into the terminal.

ghostel-readonly-enter-hook runs after entering copy or Emacs mode.
evil-ghostel uses it to switch insert state to normal state, which
covers every entry path: C-c C-t, Emacs mode, prompt and link jumps,
mouse selection, and search / minibuffer landings.  Emacs state keeps
the fast exit.

The evil read-only elate suite covers C-c C-t and isearch from insert
state.  The word-boundaries suite, documented but never added, starts
each double-click in insert state and checks that the resulting visual
selection copies exactly the selected text.

Supersedes #670.