Check for _MSC_VER definedness in libtiff code.

This avoids warnings about _MSC_VER being undefined when it's compared with
1500 when building with gcc.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73476 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix harmless g++ warning about operator precedence.

Add parentheses to suppress "&& inside ||" warning.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73477 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix harmless warning about NULL in wxStyledTextCtrl code.

Cast NULL to the type of third argument of SendMsg() explicitly to avoid a
warning about it from Ubuntu g++ 4.6.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73478 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775