runtime(doc): Fix typos in several documents (#13420)

* Fix typos in several documents
* Update runtime/doc/terminal.txt

Co-authored-by: K.Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index d5aa79e..b407631 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -877,7 +877,8 @@
 	srand()			initialize seed used by rand()
 
 Variables:						*var-functions*
-	instanceof()		check if a variable is an instance of a given class
+	instanceof()		check if a variable is an instance of a given
+				class
 	type()			type of a variable as a number
 	typename()		type of a variable as text
 	islocked()		check if a variable is locked