Add missing require 'autoloads for make all to start working

Worth noting that it uses deprecated autoloads lib, but offhand I
couldn't figure out how to replace it with `loaddefs-generate-batch`,
and I don't think it's even worth putting time into because nobody's
likely gonna use this anyway. Let's just fix the make rule because
it's easy to.

Author: Hi-Angel

Makefile

@@ -90,6 +90,7 @@ $(AUTOLOADS): $(ELFILES) purescript-mode.elc
 	$(BATCH) \
 		--eval '(setq make-backup-files nil)' \
 		--eval '(setq generated-autoload-file "$(CURDIR)/$@")' \
+		--eval "(require 'autoload)" \
 		-f batch-update-autoloads "."
 
 # HACK: embed version number into .elc file