Add automatic dependency generation.

Makefile

@@ -6,13 +6,13 @@ BISON = bison
 OBJS = dtc.o livetree.o flattree.o data.o treesource.o fstree.o \
 	dtc-parser.tab.o lex.yy.o
 
-all: $(TARGETS)
+DEPFILES = $(OBJS:.o=.d)
+
+all: $(DEPFILES) $(TARGETS)
 
 dtc:	$(OBJS)
 	$(LINK.c) -o $@ $^
 
-$(OBJS): dtc.h
-
 dtc-parser.tab.c dtc-parser.tab.h dtc-parser.output: dtc-parser.y
 	$(BISON) -d -v $<
 
@@ -21,8 +21,6 @@ lex.yy.c: dtc-lexer.l
 
 lex.yy.o: lex.yy.c dtc-parser.tab.h
 
-livetree.o:	flat_dt.h
-
 check: all
 	cd tests && $(MAKE) check
 
@@ -30,5 +28,10 @@ clean:
 	rm -f *~ *.o a.out core $(TARGETS)
 	rm -f *.tab.[ch] lex.yy.c
 	rm -f *.i *.output vgcore.*
+	rm -f *.d
 	cd tests && $(MAKE) clean
 
+%.d: %.c
+	$(CC) -MM -MG -MT "$*.o $@" $< > $@
+
+-include $(DEPFILES)