Fix off-by-one error introduced in r77483. I have a test for this, but it…

Fix off-by-one error introduced in r77483.  I have a test for this, but it currently fails due to a different dtoa.c bug;  I'll add the test once that bug is fixed.

Python/dtoa.c

@@ -1303,7 +1303,7 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
         if (dd)
             goto ret;
         if (!b->x[0] && b->wds == 1) {
-            if (i < nd)
+            if (i < nd - 1)
                 dd = 1;
             goto ret;
         }
@@ -1319,7 +1319,7 @@ bigcomp(U *rv, const char *s0, BCinfo *bc)
         if (dd)
             goto ret;
         if (!b->x[0] && b->wds == 1) {
-            if (i < nd)
+            if (i < nd - 1)
                 dd = 1;
             goto ret;
         }