guarding against deleted 'self' during the mouse handler, setting peer ptr to NULL during destruction

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76579 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Don't use the deprecated 'register' storage specifier.

It is not only useless with any modern C++ compiler, but also deprecated
in C++11.  Removing it fixes Clang warnings on the subject.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76580 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix wxOSX warnings about unused variables.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76581 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add missing Language: header to locale/msw/it.po.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76585 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Merge remote-tracking branch 'upstream/master'