Avoid duplicate octal warning during heredoc scan ahead

Author: nikic

Zend/tests/warning_during_heredoc_scan_ahead.phpt

@@ -6,6 +6,7 @@ No warnings should be thrown during heredoc scan-ahead
 <<<TEST
 ${x
}
 \400
+${"\400"}
 ${/*}
 TEST;
 
@@ -15,6 +16,8 @@ Warning: Unexpected character in input:  '
' (ASCII=1) state=0 in %s on line %d
 
 Warning: Octal escape sequence overflow \400 is greater than \377 in %s on line %d
 
+Warning: Octal escape sequence overflow \400 is greater than \377 in %s on line %d
+
 Warning: Unterminated comment starting line %d in %s on line %d
 
 Parse error: syntax error, unexpected end of file in %s on line %d