Make expat's configure detect if -ext o is needed (MW) so tests work correctly.

Had to move the CC test earlier for this to work, thus the huge configure changes.  Did use autoconf 2.57 though so it matches perfectly otherwise.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@33062 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775