Don't allocate way too much memory in wxVector::reserve().

We multiplied the number of items by the size of each element twice, once in
wxVector::reserve() itself and once in Ops::Realloc() it called, so we
allocated much more memory than actually needed.

Fix this by passing the number of elements to Ops::Realloc().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@75245 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775