makefile tidying up

Makefile

@@ -12,7 +12,9 @@ continuous:
 
 clean:
 	$(LATEXMK) -C book
-	rm -f book.log book.aux book.bbl book.lof book.out book.toc book.blg book.pdf book.ilg book.ind book.lot book.run.xml book.bcf book.fls book.fdb_latexmk authors.idx authors.ilg authors.ind subject.idx subject.ilg subject.ind
+	rm -f book.pdf *.log *.aux *.bbl *.lof *.out *.toc *.blg *.ilg *.ind \
+	      *.lot *.run.xml *.bcf *.fls *.fdb_latexmk *.idx *.ilg *.ind \
+	      *.idx *.ilg *.ind
 
 # Build with a fixed snapshot of NixPkgs 17.03.  Known-to-work.
 # For a very clean version, run git clean -fxd followed by this: