patch 8.2.2829: some comments are not correct or clear

Problem:    Some comments are not correct or clear.
Solution:   Adjust the comments.  Add test for cursor position.

src/testdir/test_exec_while_if.vim

@@ -1,6 +1,6 @@
-" Test for :execute, :while and :if
+" Test for :execute, :while, :for and :if
 
-function Test_exec_while_if()
+func Test_exec_while_if()
   new
 
   let i = 0
@@ -50,6 +50,6 @@ function Test_exec_while_if()
         \ "7x999999999888888887777777666666555554444333221",
         \ "8",
         \ "9x"], getline(1, 10))
-endfunction
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab