Fix tokenizer: backslashes sometimes led to newline token generation

parso/python/tokenize.py

@@ -483,7 +483,7 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
                 break
             initial = token[0]
 
-            if new_line and initial not in '\r\n#':
+            if new_line and initial not in '\r\n\\#':
                 new_line = False
                 if paren_level == 0 and not fstring_stack:
                     i = 0

test/fuzz_diff_parser.py

@@ -40,7 +40,7 @@ _python_reserved_strings = tuple(
 )
 _random_python_fragments = _python_reserved_strings + (
     ' ', '\t', '\n', '\r', '\f', 'f"', 'F"""', "fr'", "RF'''", '"', '"""', "'",
-    "'''", ';', ' some_random_word ', '\\'
+    "'''", ';', ' some_random_word ', '\\', '#',
 )
 
 
@@ -172,6 +172,7 @@ class FileTests:
             code = f.read()
         self._code_lines = split_lines(code, keepends=True)
         self._test_count = test_count
+        self._code_lines = self._code_lines[:30]
         self._change_count = change_count
 
         with open(file_path) as f:

test/test_tokenize.py

@@ -312,3 +312,9 @@ def test_form_feed():
 def test_carriage_return():
     lst = _get_token_list(' =\\\rclass')
     assert [t.type for t in lst] == [INDENT, OP, DEDENT, NAME, ENDMARKER]
+
+
+def test_backslash():
+    code = '\\\n# 1 \n'
+    endmarker, = _get_token_list(code)
+    assert endmarker.prefix == code