Make sure the files using version.h depend on it being generated first.

Gentoo-bug: 594586

--- a/Makefile
+++ b/Makefile
@@ -59,7 +59,7 @@
 
 all: sslh $(MAN) echosrv
 
-.c.o: *.h
+%.o: %.c *.h version.h
 	$(CC) $(CFLAGS) $(CPPFLAGS) -c $<
 
 version.h: