Open file from this source.
virtual CL_IODevice CL_VirtualFileSource::open_file( const CL_String & filename, CL_File::OpenMode mode = CL_File::open_existing , unsigned int access = CL_File::access_read | CL_File::access_write , unsigned int share = CL_File::share_all , unsigned int flags = 0);
Detailed description:
param: filename = The filename to use param: mode = CL_File::OpenMode modes param: access = CL_File::AccessFlags flags param: share = CL_File::ShareFlags flags param: flags = CL_File::Flags flags