patch 8.1.0985: crash with large number in regexp

Problem:    Crash with large number in regexp. (Kuang-che Wu)
Solution:   Check for long becoming negative int. (closes #)
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index 5cf70d4..d32369d 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -1212,13 +1212,36 @@
   call Incsearch_cleanup()
 endfunc
 
-func Test_large_hex_chars()
+func Test_large_hex_chars1()
   " This used to cause a crash, the character becomes an NFA state.
   try
     /\%Ufffffc23
   catch
     call assert_match('E678:', v:exception)
   endtry
+  try
+    set re=1
+    /\%Ufffffc23
+  catch
+    call assert_match('E678:', v:exception)
+  endtry
+  set re&
+endfunc
+
+func Test_large_hex_chars2()
+  " This used to cause a crash, the character becomes an NFA state.
+  try
+    /[\Ufffffc1f]
+  catch
+    call assert_match('E486:', v:exception)
+  endtry
+  try
+    set re=1
+    /[\Ufffffc1f]
+  catch
+    call assert_match('E486:', v:exception)
+  endtry
+  set re&
 endfunc
 
 func Test_one_error_msg()