Subject: bug#24455: 25.1.50; No error if --with-imagemagick not obeyed

From: Óscar Fuentes <[email-masked]>
Date: Sun, 18 Sep 2016 02:46:15 +0200

If we require ImageMagick support with --with-imagemagick and no usable
Imagemagick is found, the configuration will carry on.

IMO if the user requires a feature and that requirement can't be obeyed,
an error should be thrown and configuration should stop.

In GNU Emacs 25.1.50.7 (x86_64-pc-linux-gnu, X toolkit)
 of 2016-09-08 built on qcore
Repository revision: 3b3bc36b0d0b273534cf08a51d6a10c015875e2c
Windowing system distributor 'The X.Org Foundation', version 11.0.11803000
System Description:	Ubuntu 16.04.1 LTS