Change global const handling to silently ignore redeclarations

test/mjsunit/global-const-var-conflicts.js

Index: test/mjsunit/global-const-var-conflicts.js
diff --git a/test/mjsunit/global-const-var-conflicts.js b/test/mjsunit/global-const-var-conflicts.js
index d38d0ee8134fae04a730cf45071bc53e55f4983b..ac9db0054e59b5cbfd9bc8c7ede4f6df01c465b8 100644
--- a/test/mjsunit/global-const-var-conflicts.js
+++ b/test/mjsunit/global-const-var-conflicts.js
@@ -26,7 +26,7 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Check that dynamically introducing conflicting consts/vars
-// leads to exceptions.
+// is silently ignored (and does not lead to exceptions).
 
 var caught = 0;
 
@@ -54,4 +54,4 @@ assertEquals(0, d);
 try { eval("const d = 1"); } catch (e) { caught++; assertTrue(e instanceof TypeError); }
 assertEquals(0, d);
 
-assertEquals(8, caught);
+assertEquals(0, caught);