Cycles Bake: use size_t instead of width, height

(original patch by Sergey Sharybin)

Note: RNA API can't use size_t at the moment. Once it does this patch
can be tweaked a bit to fully benefit from size_t larger dimensions.
(right now num_pixels is passed as int)

Reviewed By: sergey, campbellbarton
Differential Revision: https://developer.blender.org/D688

intern/cycles/blender/blender_python.cpp

@@ -179,7 +179,7 @@ static PyObject *bake_func(PyObject *self, PyObject *args)
 
 	python_thread_state_save(&session->python_thread_state);
 
-	session->bake(b_object, pass_type, b_bake_pixel, num_pixels, depth, (float *)b_result);
+	session->bake(b_object, pass_type, b_bake_pixel, (size_t)num_pixels, depth, (float *)b_result);
 
 	python_thread_state_restore(&session->python_thread_state);