Fix reading of BitString nodes

The node tokenizer went out of its way to store BitString node values
without the leading 'b'.  But everything else in the system stores the
leading 'b'.  This would break if a BitString node is
read-printed-read.

Also, the node tokenizer didn't know that BitString node tokens could
also start with 'x'.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/4159834.1657405226@sss.pgh.pa.us

src/backend/nodes/read.c

@@ -288,7 +288,7 @@ nodeTokenType(const char *token, int length)
 		retval = T_Boolean;
 	else if (*token == '"' && length > 1 && token[length - 1] == '"')
 		retval = T_String;
-	else if (*token == 'b')
+	else if (*token == 'b' || *token == 'x')
 		retval = T_BitString;
 	else
 		retval = OTHER_TOKEN;
@@ -471,11 +471,10 @@ nodeRead(const char *token, int tok_len)
 			break;
 		case T_BitString:
 			{
-				char	   *val = palloc(tok_len);
+				char	   *val = palloc(tok_len + 1);
 
-				/* skip leading 'b' */
-				memcpy(val, token + 1, tok_len - 1);
-				val[tok_len - 1] = '\0';
+				memcpy(val, token, tok_len);
+				val[tok_len] = '\0';
 				result = (Node *) makeBitString(val);
 				break;
 			}