patch 8.0.0708: some tests are old style

Problem:    Some tests are old style.
Solution:   Change a few tests from old style to new style. (pschuh,
            closes #1813)
diff --git a/src/testdir/test_comparators.vim b/src/testdir/test_comparators.vim
new file mode 100644
index 0000000..87be006
--- /dev/null
+++ b/src/testdir/test_comparators.vim
@@ -0,0 +1,9 @@
+function Test_Comparators()
+  try
+    let oldisident=&isident
+    set isident+=#
+    call assert_equal(1, 1 is#1)
+  finally
+    let &isident=oldisident
+  endtry
+endfunction