%define token.prefix.

Provide a means to add a prefix to the name of the tokens as output in the
generated files.  Because of name clashes, it is good to have such a
prefix such as TOK_ that protects from names such as EOF, FILE etc.
But it clutters the grammar itself.

	* data/bison.m4 (token.prefix): Empty by default.
	* data/c.m4 (b4_token_enum, b4_token_define): Use it.
	* data/lalr1.cc (b4_symbol): Ditto.

data/bison.m4

@@ -542,6 +542,13 @@ m4_define([b4_percent_code_ifdef],
 	  [$3])])
 
 
+# Default values for %define.
+# ---------------------------
+# If the %token.prefix, it is empty.
+m4_percent_define_default([[token.prefix]], [[]])
+
+
+
 ## ----------------------------------------------------------- ##
 ## After processing the skeletons, check that all the user's   ##
 ## %define variables and %code qualifiers were used by Bison.  ##