cex: factor the handling of graphical symbols

* src/glyphs.h, src/glyphs.c: New.

src/glyphs.h

@@ -0,0 +1,34 @@
+/* Graphical symbols.
+
+   Copyright (C) 2020 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 GLYPHS_H
+# define GLYPHS_H
+
+/* Initialize the following variables.  */
+void glyphs_init (void);
+
+/* "→", separates the lhs of a rule from its rhs.  */
+extern const char *arrow;
+extern int arrow_width;
+
+/* "•", a point in an item (aka, a dotted rule).  */
+extern const char *dot;
+extern int dot_width;
+
+#endif /* GLYPHS_H */