Don't crash on OS X on exit if -NS* argument used

When converting argv[] from char* to wchar_t* in ConvertArgsToUnicode(),
keep an extra (shallow) copy of argc and the argv[] array so that it can
be safely freed in FreeConvertedArgs().

The reason is that other functions such as wxApp::Initialize() may
modify argv[] and remove some arguments from it; this is indeed exactly
what wxOSX does. After such changes, gs_initData.argv would no longer be
in the original state and could contain e.g. duplicate pointers or be
missing some of the pointers that we should free.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@78256 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775