mention OpenBSD and /usr/include fixes

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@17237 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -170,6 +170,14 @@ wxThread and related classes:
 OTHER CHANGES
 =============
 
+2.4.0
+-----
+
+Unix (Base/GUI):
+
+- minor OpenBSD compilation/linking fixes, now builds OOB under OpenBSD 3.1
+- don't include -I/usr/include nor -I/usr/local/include in wx-config output
+
 2.3.3
 -----