lang: parser, funcs: Change the logical operators to OR, AND, NOT

This makes it easier to read for some, and easier to parse for us. This
also frees up more characters to use elsewhere.

examples/lang/readonlyfriday.mcl

@@ -9,7 +9,7 @@ $s1 = template("Hello! It is now: {{ datetime_print . }}\n", $now)
 $s2 = if $is_friday {
 	"It's friday!!! (don't break anything, read-only)"
 } else {
-	if $day == "saturday" || $day == "sunday" {
+	if $day == "saturday" or $day == "sunday" {
 		"It's the weekend!"
 	} else {
 		fmt.printf("Unfortunately, it is %s. Go to work!", $day)