Remove unused field.

Parser/tokenizer.h

@@ -43,7 +43,6 @@ struct tok_state {
 	int decoding_state;	/* -1:decoding, 0:init, 1:raw */
 	int decoding_erred;	/* whether erred in decoding  */
 	int read_coding_spec;	/* whether 'coding:...' has been read  */
-	int issued_encoding_warning; /* whether non-ASCII warning was issued */
 	char *encoding;
 	int cont_line;          /* whether we are in a continuation line. */
 #ifndef PGEN