patch 8.2.5057: using gettimeofday() for timeout is very inefficient

Problem:    Using gettimeofday() for timeout is very inefficient.
Solution:   Set a platform dependent timer. (Paul Ollis, closes #10505)
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index e1a62bd..b354a2f 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1550,6 +1550,32 @@
   bwipe!
 endfunc
 
+func Test_search_timeout()
+  new
+  let pattern = '\%#=1a*.*X\@<=b*'
+  let search_timeout = 0.02
+  let slow_target_timeout = search_timeout * 15.0
+
+  for n in range(40, 400, 30)
+      call setline(1, ['aaa', repeat('abc ', n), 'ccc'])
+      let start = reltime()
+      call search(pattern, '', 0)
+      let elapsed = reltimefloat(reltime(start))
+      if elapsed > slow_target_timeout
+          break
+      endif
+  endfor
+  call assert_true(elapsed > slow_target_timeout)
+
+  let max_time = elapsed / 2.0
+  let start = reltime()
+  call search(pattern, '', 0, float2nr(search_timeout * 1000))
+  let elapsed = reltimefloat(reltime(start))
+  call assert_true(elapsed < max_time)
+
+  bwipe!
+endfunc
+
 func Test_search_display_pattern()
   new
   call setline(1, ['foo', 'bar', 'foobar'])