patch 8.2.0258: modifyOtherKeys cannot be temporarily disabled

Problem:    ModifyOtherKeys cannot be temporarily disabled.
Solution:   Add echoraw() with an example for modifyOtherKeys.
diff --git a/src/testdir/dumps/Test_functions_echoraw.dump b/src/testdir/dumps/Test_functions_echoraw.dump
new file mode 100644
index 0000000..f27cd03
--- /dev/null
+++ b/src/testdir/dumps/Test_functions_echoraw.dump
@@ -0,0 +1,5 @@
+>x+0&#ffffff0|e|l@1|o| @34
+|~+0#4040ff13&| @38
+|~| @38
+|~| @38
+| +0#0000000&@21|0|,|0|-|1| @8|A|l@1| 
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 9173e85..c748854 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -2,6 +2,7 @@
 source shared.vim
 source check.vim
 source term_util.vim
+source screendump.vim
 
 " Must be done first, since the alternate buffer must be unset.
 func Test_00_bufexists()
@@ -2017,3 +2018,19 @@
   " uniq()
   call assert_equal([0, 1, 2, 3, 4], uniq(range(5)))
 endfunc
+
+func Test_echoraw()
+  CheckScreendump
+
+  " Normally used for escape codes, but let's test with a CR.
+  let lines =<< trim END
+    call echoraw("hello\<CR>x")
+  END
+  call writefile(lines, 'XTest_echoraw')
+  let buf = RunVimInTerminal('-S XTest_echoraw', {'rows': 5, 'cols': 40})
+  call VerifyScreenDump(buf, 'Test_functions_echoraw', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('XTest_echoraw')
+endfunc