[es6] Initial support for let/const bindings in sloppy mode

test/mjsunit/harmony/block-let-declaration-sloppy.js

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 // Test let declarations in various settings.
 
-"use strict";
+// Flags: --no-legacy-const --harmony-sloppy
 
 // Global
 let x;
 let y = 2;
 const z = 4;
 
 // Block local
 {
   let y;
   let x = 3;
@@ skipping 107 matching lines @@
 
 // Test function declarations in statement position in strict mode.
 TestLocalThrows("function f() { if (true) function g() {} }", SyntaxError);
 TestLocalThrows("function f() { if (true) {} else function g() {} }", SyntaxError);
 TestLocalThrows("function f() { do function g() {} while (false) }", SyntaxError);
 TestLocalThrows("function f() { while (false) function g() {} }", SyntaxError);
 TestLocalThrows("function f() { label: function g() {} }", SyntaxError);
 TestLocalThrows("function f() { for (;false;) function g() {} }", SyntaxError);
 TestLocalDoesNotThrow("function f() { switch (true) { case true: function g() {} } }");
 TestLocalDoesNotThrow("function f() { switch (true) { default: function g() {} } }");