CLEANUP: assorted typo fixes in the code and comments

These are mostly comments in the code. A few error messages were fixed
and are of low enough importance not to deserve a backport. Some regtests
were also fixed.
diff --git a/reg-tests/mailers/healthcheckmail.lua b/reg-tests/mailers/healthcheckmail.lua
index 9c75877..50b561c 100644
--- a/reg-tests/mailers/healthcheckmail.lua
+++ b/reg-tests/mailers/healthcheckmail.lua
@@ -93,7 +93,7 @@
 			end
 		end
 	end
-	core.Info("#### Body recieved OK")
+	core.Info("#### Body received OK")
 	applet:send("250 OK\r\n")
 
 	if RecieveAndCheck(applet, "QUIT") == false then