wxString::To(U)LongLong has very bad semantics, if that function is not supported on a given platform, it silently fails. Took me hours to spot this as the cause for a strange bug in one of my programs. While not fixing the silent failure (e.g. via #error), this patch adds support for additional platforms.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@76634 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775