bug#22356: 25.0.50; emacs-25 very crashy with ivy-mode

[Dmitry Gutov]

Possibly as a result of some recent ivy-mode update, Emacs crashes quite
promptly when I use it. I've tried going back a couple of days in Emacs
revisions, and the problem is also there.

Here are a few xbacktrace-s (I think 3-5 are from an earlier revision,
but 1-2 should be from this one). Let me know if 'bt full' is needed.
I'll be doing 'git bisect' next.

highlight-tail-mode features in some of them, too, but it's fairly
stable when not in conjunction with ivy-mode. E.g., it's currently
enabled in this email buffer.

crash1.log
Description: Text document

crash2.log
Description: Text document

crash3.log
Description: Text document

crash4.log
Description: Text document

crash5.log
Description: Text document

In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.16.7)
 of 2016-01-12 built on axl
Repository revision: 1f6898d0510cd15455f665c0f38451755a374243
Windowing system distributor 'The X.Org Foundation', version 11.0.11702000
System Description:     Ubuntu 15.10

Configured using:
 'configure --enable-checking=yes,glyphs --enable-check-lisp-object-type
 'CFLAGS=-O0 -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS NOTIFY
GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11

Important settings:
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix