have parser trap const declaration without value (#2756)

fixes #2751

lib/parse.js

@@ -1862,7 +1862,7 @@ function parse($TEXT, options) {
                     name  : as_symbol(sym_type),
                     value : is("operator", "=")
                         ? (next(), expression(false, no_in))
-                        : !no_in && kind === "const" && S.input.has_directive("use strict")
+                        : !no_in && kind === "const"
                             ? croak("Missing initializer in const declaration") : null,
                     end   : prev()
                 });