Add test for passing in define macro without a value to distutils

via distutils comment directives in a Cython source file.

tests/run/define_macro.pyx

+#distutils: define_macros = DEFINE_NO_VALUE, DEFINE_WITH_VALUE=0
+
+cdef extern from "define_macro_helper.h" nogil:
+    int VAL;
+
+def test():
+    """
+    >>> test()
+    1
+    """
+    return VAL

tests/run/define_macro_helper.h

+#pragma once
+#ifdef DEFINE_NO_VALUE
+#define VAL (DEFINE_WITH_VALUE + 1)
+#else
+#define VAL DEFINE_WITH_VALUE
+#endif