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/ex_cmds.c b/src/ex_cmds.c
index c8a93bc..881e6f9 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -5288,7 +5288,7 @@
  * Return a heuristic indicating how well the given string matches.  The
  * smaller the number, the better the match.  This is the order of priorities,
  * from best match to worst match:
- *	- Match with least alpha-numeric characters is better.
+ *	- Match with least alphanumeric characters is better.
  *	- Match with least total characters is better.
  *	- Match towards the start is better.
  *	- Match starting with "+" is worse (feature instead of command)