Added support for generating dependencies for idl files.

include/Makefile.in

diff --git a/include/Makefile.in b/include/Makefile.in
index 1ba793e..e47f873 100644
--- a/include/Makefile.in
+++ b/include/Makefile.in
@@ -175,6 +175,7 @@
 	wshisotp.h \
 	wsipx.h \
 	zmouse.h \
+	$(IDL_SRCS) \
 	$(IDL_SRCS:.idl=.h)
 
 MSVCRT_INCLUDES = \
@@ -252,8 +253,6 @@
 .idl.h:
 	$(LDPATH) $(WIDL) $(DEFS) -b -h -H $@ $<
 
-$(IDL_SRCS:.idl=.h): $(WIDL)
-
 .PHONY: idl
 
 idl: $(IDL_SRCS:.idl=.h)