Make sure that tests/seek_test.o gets deleted on 'make clean'.

Closes issue 1273.

Originally committed as revision 19458 to svn://svn.ffmpeg.org/ffmpeg/trunk

Makefile

@@ -121,7 +121,7 @@ clean:: testclean
 	rm -f $(ALLPROGS) $(ALLPROGS_G)
 	rm -f $(CLEANSUFFIXES)
 	rm -f doc/*.html doc/*.pod doc/*.1
-	rm -f tests/seek_test$(EXESUF)
+	rm -f tests/seek_test$(EXESUF) tests/seek_test.o
 	rm -f $(addprefix tests/,$(addsuffix $(HOSTEXESUF),audiogen videogen rotozoom tiny_psnr))
 	rm -f $(addprefix tools/,$(addsuffix $(EXESUF),cws2fws pktdumper qt-faststart trasher))