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/charset.c b/src/charset.c
index 7505fea..aa843d1 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1939,7 +1939,7 @@
 	}
     }
 
-    // Check for an alpha-numeric character immediately following, that is
+    // Check for an alphanumeric character immediately following, that is
     // most likely a typo.
     if (strict && n - 1 != maxlen && ASCII_ISALNUM(*ptr))
 	return;