Add option imagemagick-types-enable

* lisp/image.el: For clarity, call imagemagick-register-types at
top-level, rather than relying on a custom :initialize.
(imagemagick-types-enable): New option. 
(imagemagick-register-types): Respect imagemagick-types-inhibit.
If disabling support, remove elements altogether rather
than using an impossible regexp.
(imagemagick-types-inhibit): Give it the default init function.

* src/image.c (Fimagemagick_types): Doc fix.

* etc/NEWS: Mention this.

Fixes: debbugs:11557

1 files changed, 4 insertions, 2 deletions

diff --git a/src/image.c b/src/image.c
index a3b64b74997..b6cdb6c8290 100644
--- a/src/image.c
+++ b/src/image.c
@@ -1,5 +1,6 @@
 /* Functions for image support on window system.
-   Copyright (C) 1989, 1992-2012 Free Software Foundation, Inc.
+
+Copyright (C) 1989, 1992-2012 Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
 
@@ -7987,7 +7988,8 @@ their descriptions (http://www.imagemagick.org/script/formats.php).
 You can also try the shell command: `identify -list format'.
 
 Note that ImageMagick recognizes many file-types that Emacs does not
-recognize as images, such as C.  See `imagemagick-types-inhibit'.  */)
+recognize as images, such as C.  See `imagemagick-types-enable'
+and `imagemagick-types-inhibit'.  */)
   (void)
 {
   Lisp_Object typelist = Qnil;