Only return -1,0,1 from wxXmlResource::CompareVersion().

In other words, do as the comment says.  Also fixes an implicit
conversion warning.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74472 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix lots of warnings reported by Clang.

Mostly potentially lossy implicit conversions in headers (long->int). Also dangling else warnings. Struct/class mismatches.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74473 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775