[dcl.init] Add index entry for direct-initialization. (#1491)

Author: Eelis

source/declarators.tex

@@ -2760,7 +2760,7 @@
 \grammarterm{mem-initializer}{s}~(\ref{class.base.init}), and
 the \grammarterm{braced-init-list} form of a \grammarterm{condition}
 is called
-\grammarterm{direct-initialization}.
+\defn{direct-initialization}.
 
 \pnum
 The semantics of initializers are as follows.