Fix #79934: CRLF-only line in heredoc causes parsing error

Fixes the function `next_newline()` in zend_language_scanner.l. The
function now correctly returns a newline_len of 2 for "\r\n".

Closes GH-5944.

Author: pevdh

NEWS

@@ -9,6 +9,8 @@ PHP                                                                        NEWS
   . Fixed bug #79895 (PHP_CHECK_GCC_ARG does not allow flags with equal sign).
     (Santiago M. Mola)
   . Fixed bug #79919 (Stack use-after-scope in define()). (cmb)
+  . Fixed bug #79934 (CRLF-only line in heredoc causes parsing error).
+    (Pieter van den Ham)
 
 - LDAP:
   . Fixed memory leaks. (ptomulik)

Zend/tests/bug79934.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Bug #79934: CRLF-only line in heredoc causes parsing error
+--DESCRIPTION--
+This test covers different variations of whitespace-only lines in heredoc strings.
+These whitespace-only lines should be ignored when stripping indentation.
+--FILE--
+<?php
+// lines with only CRLF should not cause a parse error
+eval("\$s1 = <<<HEREDOC\r\n    a\r\n\r\n    b\r\n    HEREDOC;");
+var_dump(addcslashes($s1, "\r\n"));
+
+// lines with only a LF should not cause a parse error
+eval("\$s2 = <<<HEREDOC\n    a\n\n    b\n    HEREDOC;");
+var_dump(addcslashes($s2, "\n"));
+
+// lines with only a CR should not cause a parse error
+eval("\$s3 = <<<HEREDOC\r    a\r\r    b\r    HEREDOC;");
+var_dump(addcslashes($s3, "\r"));
+
+// lines with only whitespace should not cause a parse error
+eval("\$s4 = <<<HEREDOC\r    a\r\n  \r\n    b\r    HEREDOC;");
+var_dump(addcslashes($s4, "\n\r"));
+
+?>
+--EXPECT--
+string(10) "a\r\n\r\nb"
+string(6) "a\n\nb"
+string(6) "a\r\rb"
+string(10) "a\r\n\r\nb"