Add wxCondition::Wait() overload that also tests the condition.

Add wxCondition::Wait() overload that also tests the condition.

Add Wait() overload that takes a functor argument and doesn't return
until the condition is signaled _and_ the predicate returns true.  This
is useful for dealing with spurious wakeups and is modeled after C++11
std::condition_variable's corresponding method.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74771 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775