patch 8.0.1809: various typos

Problem:    Various typos.
Solution:   Correct the mistakes, change "cursur" to "cursor". (closes #2887)
diff --git a/src/edit.c b/src/edit.c
index 9b72064..ef4c98d 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -431,7 +431,7 @@
 #ifdef FEAT_CONCEAL
     /* Check if the cursor line needs redrawing before changing State.  If
      * 'concealcursor' is "n" it needs to be redrawn without concealing. */
-    conceal_check_cursur_line();
+    conceal_check_cursor_line();
 #endif
 
 #ifdef FEAT_MOUSE