Proper quoting for install man.

Index: findlib-1.6.1/Makefile
===================================================================
--- findlib-1.6.1.orig/Makefile
+++ findlib-1.6.1/Makefile
@@ -71,7 +71,7 @@ findlib.conf: findlib.conf.in
 
 .PHONY: install-doc
 install-doc:
-	mkdir -p "$(prefix)$(OCAMLFIND_MAN)/man1" "$(prefix)$(OCAMLFIND_MAN)/man3 $(prefix)$(OCAMLFIND_MAN)/man5"
+	mkdir -p "$(prefix)$(OCAMLFIND_MAN)/man1" "$(prefix)$(OCAMLFIND_MAN)/man3" "$(prefix)$(OCAMLFIND_MAN)/man5"
 	-cp doc/ref-man/ocamlfind.1 "$(prefix)$(OCAMLFIND_MAN)/man1"
 	-cp doc/ref-man/META.5 doc/ref-man/site-lib.5 doc/ref-man/findlib.conf.5 "$(prefix)$(OCAMLFIND_MAN)/man5"