Crashes under Windows due to pointer-to-long cast

[bertholet]

I consistently got system crashes on my system with Matlab 2016b,windows10, visual studio 2013 c++. The problem is that longs have only 4 Byte in VS and casting pointers to long breaks them. Could fix it by replacing long by intptr_t,

[taiya]

feel free to create a pull request!

[taiya]

Thanks for your pull request!

[bertholet]

No worries, and thank you for the handy implementation(;