patch 8.2.0156: various typos in source files and tests

Problem:    Various typos in source files and tests.
Solution:   Fix the typos. (Emir Sari, closes #5532)
diff --git a/src/testdir/test_cindent.vim b/src/testdir/test_cindent.vim
index 2d78be1..dfafd01 100644
--- a/src/testdir/test_cindent.vim
+++ b/src/testdir/test_cindent.vim
@@ -815,7 +815,7 @@
         }
      }
 
-  public: // <-- this was incorectly indented before!!
+  public: // <-- this was incorrectly indented before!!
      void testfall();
   protected:
      void testfall();
@@ -1780,7 +1780,7 @@
   		}
   	}
 
-  	public: // <-- this was incorectly indented before!!
+  	public: // <-- this was incorrectly indented before!!
   	void testfall();
   	protected:
   	void testfall();
@@ -5254,9 +5254,12 @@
 " this was going beyond the end of the line.
 func Test_cindent_case()
   new
-  call setline(1, "case x: // x")
+  call setline(1, 'case x: // x')
   set cindent
   norm! f:a:
+  call assert_equal('case x:: // x', getline(1))
+
+  set cindent&
   bwipe!
 endfunc