style: rename LR0.* as lr0.*

Let's stick to lower case for file names.

* src/LR0.h, src/LR0.c: Rename as...
* src/lr0.h, src/lr0.c: these.

src/lr0.h

@@ -0,0 +1,28 @@
+/* Generate the LR(0) parser states for Bison.
+
+   Copyright (C) 1984, 1986, 1989, 2000-2002, 2009-2015, 2018-2019 Free
+   Software Foundation, Inc.
+
+   This file is part of Bison, the GNU Compiler Compiler.
+
+   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 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef LR0_H_
+# define LR0_H_
+
+# include "state.h"
+
+void generate_states (void);
+
+#endif /* !LR0_H_ */