allow show_token() on TOKEN_ZERO_IDENT

TOKEN_ZERO_IDENTs are created during the evaluation of pre-processor
expressions but which otherwise are normal idents and  were first tokenized
as TOKEN_IDENTs.

As such, they could perfectly be displayed by show_token() but are not.
So, in error messages they are displayed as "unhandled token type '4'",
which is not at all informative.

Fix this by letting show_token() process them like usual TOKEN_IDENTs.
Idem for quote_token().

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: lucvoo

tokenize.c

@@ -201,6 +201,7 @@ const char *show_token(const struct token *token)
 		return "end-of-input";
 
 	case TOKEN_IDENT:
+	case TOKEN_ZERO_IDENT:
 		return show_ident(token->ident);
 
 	case TOKEN_NUMBER:
@@ -259,6 +260,7 @@ const char *quote_token(const struct token *token)
 		return "syntax error";
 
 	case TOKEN_IDENT:
+	case TOKEN_ZERO_IDENT:
 		return show_ident(token->ident);
 
 	case TOKEN_NUMBER: