Rename `image-library-alist' to `dynamic-library-alist'.

Rename `image-library-alist' to `dynamic-library-alist'.

* etc/NEWS: Mention `dynamic-library-alist'.

* lisp/image.el (image-library-alist): Declare as obsolete alias.
  (image-type-available-p): Use `dynamic-library-alist'.

* lisp/term/w32-win.el (dynamic-library-alist):
  Use instead of `image-library-alist'.

* nt/INSTALL: Refer to `dynamic-library-alist'.

* src/image.c (Vimage_library_alist)
  (syms_of_image) <image-library-alist>: Move to src/emacs.c and rename.
  (lookup_image_type): Use Vdynamic_library_alist.
  (Finit_image_library): Doc fix.

* src/emacs.c (Vdynamic_library_alist)
  (syms_of_emacs) <dynamic-library-alist>: Move from src/image.c and rename.
  Doc fix.

* src/lisp.h (Vdynamic_library_alist): Declare extern.