* lib/Makefile.in (OBJEXT): Define for subst.
(OBJECTS): Use $(OBJEXT) instead of '.o'.
* src/Makefile.in: Make dependencies use $(OBJEXT).
(OBJEXT, EXEEXT): Define for subst.
(TARGETPROG): Add $(EXEEXT).
(OBJECTS): Use $(OBJEXT) instead of '.o'.
(clean): Remove *.$(OBJEXT) instead of *.o.