Fix man paths

http://bugs.gentoo.org/show_bug.cgi?id=326185

--- a/src/bin/nonbonded/Makefile.in
+++ b/src/bin/nonbonded/Makefile.in
@@ -19,5 +19,5 @@
 endif
 
 install_man:: nonbonded.1
-	$(MKDIRS) $(mandir)/man1
-	$(INSTALL_INCLUDE) $^ $(mandir)/man1
+	$(MKDIRS) $(DESTDIR)$(mandir)/man1
+	$(INSTALL_INCLUDE) $^ $(DESTDIR)$(mandir)/man1
--- a/src/bin/intder/Makefile.in
+++ b/src/bin/intder/Makefile.in
@@ -21,6 +21,6 @@
 endif
 
 install_man:: intder.1
-	$(MKDIRS) $(mandir)/man1
-	$(INSTALL_INCLUDE) $^ $(mandir)/man1
+	$(MKDIRS) $(DESTDIR)$(mandir)/man1
+	$(INSTALL_INCLUDE) $^ $(DESTDIR)$(mandir)/man1