Fix OS X compilation in C++11 mode with libc++.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74457 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
fixing forced link of quicktime backend on osx_cocoa

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74458 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775