Work around buggy printer drivers not returning correct DEVMODE size.

Apparently at least one printer driver doesn't report the memory needed by its
own DEVMODE struct correctly, resulting in a crash due to a buffer overflow
when printing using it.

Work around this by allocating slightly more memory than what we really need.

Closes #16274.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@77522 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775