add a test (Close #24)

Issue #24 has been fixed by the following commits:
 * b9fba1d
 * c1fc76b
 * a0efc0a

Segmentation fault might occur before the fix.

testpy.py

@@ -960,6 +960,7 @@ def get_text_writer(fileno, **kwargs):
     x2("\\z", "hello", 5, 5)
     x2("\\n?\\z", "こんにちは", 5, 5)
     x2("\\z", "こんにちは", 5, 5)
+    x2("()" * 32768, "", 0, 0)      # Issue #24
 
     # character classes (tests for character class optimization)
     x2("[@][a]", "@a", 0, 2);