[support.initlist] Don't claim that std::initializer_list is a type; it's a

class template.

Fixes #280.

Author: zygoloid

source/support.tex

@@ -3097,7 +3097,8 @@
 \indextext{\idxhdr{initializer\_list}}%
 \indexlibrary{\idxhdr{initializer_list}}%
 \pnum
-The header \tcode{<initializer_list>} defines one type.
+The header \tcode{<initializer_list>} defines a class template and several
+support functions related to list-initialization~(see \ref{dcl.init.list}).
 
 \synopsis{Header \tcode{<initializer_list>} synopsis}