enabled casting of const void*

include/pybind11/cast.h

@@ -389,7 +389,7 @@ public:
         return true;
     }
 
-    static handle cast(void *ptr, return_value_policy /* policy */, handle /* parent */) {
+    static handle cast(const void *ptr, return_value_policy /* policy */, handle /* parent */) {
         if (ptr)
             return capsule(ptr).release();
         else

include/pybind11/pytypes.h

@@ -451,8 +451,8 @@ class capsule : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(capsule, object, PyCapsule_CheckExact)
     capsule(PyObject *obj, bool borrowed) : object(obj, borrowed) { }
-    capsule(void *value, void (*destruct)(PyObject *) = nullptr)
-        : object(PyCapsule_New(value, nullptr, destruct), false) {
+    capsule(const void *value, void (*destruct)(PyObject *) = nullptr)
+        : object(PyCapsule_New(const_cast<void*>(value), nullptr, destruct), false) {
         if (!m_ptr) pybind11_fail("Could not allocate capsule object!");
     }
     template <typename T> operator T *() const {