cameo: migrated Excellon reader from drl2gp

- Makefile (OBJS): added excellon.o
- README: added brief description of Excellon input
- excellon.h, excellon.c: adaptation of KiCad drill file reader from
  ../drl2gp/drl2gp.c
- lang.l, lang.y: added command "excellon" to read KiCad drill files
- gerber.h: removed stray newline

cameo/excellon.h

@@ -0,0 +1,21 @@
+/*
+ * excellon.h - KiCad drill file input
+ *
+ * Written 2010 by Werner Almesberger
+ * Copyright 2010 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef EXCELLON_H
+#define EXCELLON_H
+
+#include "path.h"
+
+
+struct path *excellon_read(const char *name);
+
+#endif /* !EXCELLON_H */