Account for first removal char with wxELLIPSIZE_MIDDLE.

Account for first removal char with wxELLIPSIZE_MIDDLE.

wxControl::Ellipsize() in wxELLIPSIZE_MIDDLE mode starts the
string-shortening loop with the removal interval initially set to remove
only the len/2-th character. But it didn't add its size to the running
total of removal characters' length, thus always removing one more
character. Fixed by making the initial interval 0-sized rather than
1-sized.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66823 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775