vim-patch:8.0.0644: the timeout for 'hlsearch' is not tested

Problem:    There is no test for 'hlsearch' timing out.
Solution:   Add a test.
5b1affefd0

src/nvim/testdir/test_hlsearch.vim

@@ -32,6 +32,24 @@ function! Test_hlsearch()
   enew!
 endfunction
 
+func Test_hlsearch_hangs()
+  if !has('reltime') || !has('float')
+    return
+  endif
+
+  " This pattern takes forever to match, it should timeout.
+  help
+  let start = reltime()
+  set hlsearch nolazyredraw redrawtime=101
+  let @/ = '\%#=2\v(a|\1)*'
+  redraw
+  let elapsed = reltimefloat(reltime(start))
+  call assert_true(elapsed > 0.1)
+  call assert_true(elapsed < 1.0)
+  set nohlsearch redrawtime&
+  quit
+endfunc
+
 func Test_hlsearch_eol_highlight()
   new
   call append(1, repeat([''], 9))