Makefile: use DESTDIR, make directories if they do not exist

Signed-off-by: Christoph Lohmann <20h@r-36.net>

Makefile

@@ -17,16 +17,18 @@ bin/md2point: md2point.o
 	${CC} -c ${CFLAGS} $<
 
 install:
-	install -m755 bin/dir2point $(PREFIX)/bin/dir2point
-	install -m755 bin/md2point  $(PREFIX)/bin/md2point
-	install -m755 bin/point2pdf $(PREFIX)/bin/point2pdf
-	install -m644 md2point.1    $(MANPREFIX)/man1/md2point.1
+	mkdir -p $(DESTDIR)$(PREFIX)/bin
+	install -m 755 bin/dir2point $(DESTDIR)$(PREFIX)/bin/dir2point
+	install -m 755 bin/md2point  $(DESTDIR)$(PREFIX)/bin/md2point
+	install -m 755 bin/point2pdf $(DESTDIR)$(PREFIX)/bin/point2pdf
+	mkdir -p $(DESTDIR)$(MANPREFIX)/man1
+	install -m 644 md2point.1    $(DESTDIR)$(MANPREFIX)/man1/md2point.1
 
 uninstall:
-	rm -f $(PREFIX)/bin/dir2point
-	rm -f $(PREFIX)/bin/md2point
-	rm -f $(PREFIX)/bin/point2pdf
-	rm -f $(MANPREFIX)/man1/md2point.1
+	rm -f $(DESTDIR)$(PREFIX)/bin/dir2point
+	rm -f $(DESTDIR)$(PREFIX)/bin/md2point
+	rm -f $(DESTDIR)$(PREFIX)/bin/point2pdf
+	rm -f $(DESTDIR)$(MANPREFIX)/man1/md2point.1
 
 clean:
 	rm -f bin/md2point