Remove ATL dependency from MSMF capture code.

Current MSMF code uses WRL smart pointers if it's compiled in Win RT and SDK 8 environment and ATL smart pointers otherwise. Due to this ATL dependency it's impossible to build the module using MinGW or VS Express because they don't support ATL.
Declaring ComPtr wrapper class (mimicking WRL smart pointer) using _com_ptr_t instead of ATL's CComPtr would make this more portable.