Implement string initialization from C char

string.pxd

@@ -26,6 +26,9 @@ cdef cypclass Str "Cy_Str":
     __init__(self, const char *s):
         self._str = string(s)
 
+    __init__(self, const char c, int count = 1):
+        self._str = string(count, c)
+
     size_t __len__(self):
         return self._str.size()