Revert "A small improvement in checks"

The problem with this commit is that it probably makes some checks slower. It's
still slightly more beautiful, but we leave it for now.

This reverts commit 25e4ea9c24.

parso/python/tokenize.py

@@ -59,6 +59,10 @@ def group(*choices, **kwargs):
     return start + '|'.join(choices) + ')'
 
 
+def any(*choices):
+    return group(*choices) + '*'
+
+
 def maybe(*choices):
     return group(*choices) + '?'
 
@@ -353,7 +357,9 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0)):
                     contstr = line[start:]
                     contline = line
                     break
-            elif any(token.startswith(s) for s in single_quoted):
+            elif initial in single_quoted or \
+                    token[:2] in single_quoted or \
+                    token[:3] in single_quoted:
                 if token[-1] == '\n':                       # continued string
                     contstr_start = lnum, start
                     endprog = (endpats.get(initial) or endpats.get(token[1])