Include ac_cfg.h before libavrdude.h

On MSVC, this is required in order to have a definition of
PATH_MAX in place.

src/lexer.l

@@ -28,6 +28,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 
+#include "ac_cfg.h"
 #include "avrdude.h"
 #include "libavrdude.h"
 #include "config.h"

src/update.c

@@ -25,6 +25,7 @@
 #include <string.h>
 #include <time.h>
 
+#include "ac_cfg.h"
 #include "avrdude.h"
 #include "libavrdude.h"